# Difference between revisions of "Expression Language"

The 'Contents' box above contains a list of available functions roughly grouped by usage scenario, and each function name gives a fair indication of what it might do. Each of the group headers contain some basic information pertinent to the functions inside the group. Click on a function or function group header in the Contents box to be taken directly to more information about it on the page. At the bottom right of each section there is a "Back to top" link which will take you back up to the Contents box allowing you to quickly get to where on the page you would like to go next.
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## Overview

The J. River Media Core database engine supports Excel-style functions for use in view schemes, searches, displayed columns, and tag editing.

An expression is a mixture of text, fields, and functions. A function allows special operations to be performed. Functions are all listed with a name followed by an opening and closing parenthesis. When building expressions, the instructions you wish to pass to the function are placed inside these parenthesis, with multiple instructions separated by commas. When your expression is evaluated, any spaces entered after a comma are ignored. This allows you to compose complex expressions on multiple lines, making it easier to keep track of where you are in your expression. Occasionally, you will find that you want a space, or parenthesis character to be treated literally as part of your instructions, rather than expression syntax, and in these cases, the character is "escaped" by using a preceding forward slash. Examples using this escaping can be seen here and here. As you progress with your expression building, you will begin nesting multiple functions into a single expression; always remember that a completed expression must contain a matching number of opening and closing parenthesis in order to work reliably.

The functions available to us range from highly functional, with a broad range of applicable uses, through specialised, limited use functions that only appeal to a select group of users, to seemingly redundant functions and obscure functions that Media Center uses internally. The functions below are listed with those with the broadest appeal at the top, and the more obscure at the bottom.

Any given expression can only work on any given single file. It is not possible to compare a field in one file with a field in another file.
Batch file operations are possible, and when used in a list, even a grouped list, an expression will be applied to each individual file in turn, not as a group.

A slightly extended overview is also available elsewhere in this wiki, titled Database Expressions, and another page attempts to demonstrate Media Center mimicking the "AND", "OR" and "XOR" database searches.

## Using expressions

Expressions are ubiquitous in Media Center, and are useful in a variety of locations such as the following:

• Player Display (right-click the Player Display , choose "Customize")
• Captions & Thumbnail text
• Panes (aka Categories)
• Expression columns (right-click a column header and choose "Add expression column")
• The library field manager (Create expression-based library fields)
• Theater View
• Rename, Move, & Copy Files tool

The syntax of the expression language is generally consistent throughout Media Center. An expression is evaluated, formatting output that is used in the context where the expression was evaluated. To perform Tag assignment or Search rule filtering, an expression is modified slightly to work in these contexts.

### Formatting output

To give usage examples for all of these locations is beyond the scope of this page, so a few tips should suffice to get those interested up and running.

• Using expressions to produce custom Thumbnail text makes it possible to display only relevant or useful data.
• Expressions can be used to reduce link bar clutter by conditionally displaying links based on, for example, Media Type.
• File and directory paths may be based on expressions; this is especially useful in Options > File Locations, and in the "Rename, Move, & Copy Files" tool.
• User-specified library fields may be calculated, based on the output of expressions.

### Tag assignment

The output of an expression can be used to assign a value to a tag. This is accomplished by preceding the expression with an "=" character. The "=" character causes the tagging engine to invoke the expression evaluator first, and then to use its output as the value to assign to the tag. Without the prepended "=" character, the expression itself (and not its evaluated value) would be stored in the tag.

An assignment expression can be entered into the Tag Action Window, or by using inline editing in the file list or a pane entry.

Note: Undo is supported, reverting each tag to its value prior to the assignment. Redo is also supported, reapplying the most recent Undo.

The following screenshots illustrates using an expression for tag assignment:

 Pressing "Enter" copies the Date data into the caption field Just like that!

### Search rule filtering

Expressions can be used as search filters, and in order to do so, the expression must be entered into the search field using the following format:
[=EXPRESSION]=1 or [=EXPRESSION]=0

All files that match the expression will return "1" and all that don't match, return "0". Decide which is required and use "1" or "0" accordingly.

Remember that the search field appears in many places throughout Media Center, places that include:

• The search field itself (in the top right corner of the program)
• A view scheme search list
• "Edit Files To Show" area of the Customize View dialogue
• The last.fm submission filter

and this method of expression application can be used in all of them.

An example of an expression formatted for use in the search field would be: [=isequal(formatdate([date imported,0],MM//yyyy),formatdate(now(),MM//yyyy),1)]=1 Which will list all files that have been imported this month.

## Specify data types for expression based fields

It is often useful to force Media Center to operate on data of one type as if it were another type. This is useful for changing sort order, or handling list data as a simple string. For example, month names are sorted alphabetically by default, but by setting the data type, sorting can be chronological instead. Data types are forced by appending to an expression the string: &datatype=[DATA TYPE], where DATA TYPE is one of the following values:

• List: A list of strings, separated by semicolons
• String: Sorts as strings (with smart number handling)
• Number: Sorts values as numbers (decimal or integer)
• Integer: Sorts values as integers
• Path: Sorts using a smart filename compare style
• Month: Sorts string month names (i.e. January, February, etc.)

The following screen images show these data type instructions in action:

&DataType=[Month] &DataType=[List]
Used in a pane, formatdate([date,0],MMMM) returns the months as requested, but the alphabetic order is a little confusing.
Adding the "month" data type, like so, formatdate([date,0],MMMM)&datatype=[month], takes care of the order.

No data type has been specified, so the expression results are presented literally, as individual string values.
Add the "list" data type to the expression and it is then formatted correctly in the pane. Here, the ListBuild function has been used to create a nested browsing tree.

## Fields

Any text between brackets [] will be replaced with the corresponding field from your library. As an example, [Artist] would be replaced by Bob Dylan for any Bob Dylan tracks. If the text between brackets doesn't match any known fields, it will be left alone, [My Fake Artist] will be treated literally, square brackets and all. After the field name, a comma can be placed followed by a 0 or 1 to indicate whether the field should be formatted. So, [Duration] and [Duration, 1] will give "4:02" while [Duration, 0] will give "242". This is particularly important when working with the "Format" functions, where most times you will want the evaluator to work with the raw field contents rather than the formatted contents you see in the file list.

Function and field values in expressions are not case-sensitive. Available functions with descriptions and examples are listed below.

## Functions

### Conditional Functions

The functions in this section evaluate one or more of their arguments to determine if their result is true or false, and execute specific actions depending upon that result.

Although the expression language does not directly support AND, OR, and XOR, these can be easily emulated. See: Database_Expressions_AND_OR_And_XOR.

Beginning with version 17.0.40, Media Center supports the NOT operator (a ! character) in a conditional. This can be used to invert the sense of an If() statement for easier reading, or in an IfElse() to better support if-then-else chains.

#### If(...): Conditional If/Then/Else evaluator.

 If() This will be the function you will likely use more than any other. It is typically used in conjunction with one or more other functions and allows you to give specific instructions depending upon whether the result is positive (1) or negative (0). The positive instruction is always given first. if(expression to test,instructions if positive,instructions if negative) if(isequal([artist],bob dylan,1),Genius,Mediocre)Wherever this expression is applied, be it as an expression column or category, as part of a renaming rule, thumbnail text, if the artist tag is Bob Dylan, Media Center will produce Genius, and for all other artists, it will produce Mediocre. The "IsEqual()" function is described in the first table below. if(isequal([artist],bob dylan,1),Genius,if(isequal([album],Joshua Tree,8),Great Album,Mediocre)) Here, we have two nested "If" functions. First we ask if the artist is Bob Dylan, if the result is positive, write "Genius". If the artist is not Dylan, we then ask if the album is "Joshua Tree", if yes, write "Great Album", and if no, write mediocre if(!isempty([comment]), Regex([comment], /#^(\S+\s+\S+\s+\S+)#/, 1), *No Comment) Output's the first three words of the comment field; otherwise, outputs "*No Comment". By inverting the sense of the conditional, the more interesting case is moved ahead of the more mundane case. Take care to provide all three arguments to the If() statement, and for nested statements, to ensure the proper number of closing parenthesis. This can become less-than-obvious with nested sequences. The built-in expression editor can lessen the burden by allowing line breaks or whitespace after commas (argument separators). For example, the previous example is easier to read and maintain as: if(!isempty([comment]), Regex([comment], /#^(\S+\s+\S+\s+\S+)#/, 1), *No Comment)

#### IfElse(...): If/Then/Else sequence of conditional tests and actions.

 IfElse() The IfElse() conditional (available since build 17.0.7) provides a convenient mechanism for shortening and more clearly expressing nested conditionals into an alternating sequence of tests and actions. For example, consider a nested sequence of If() tests such as If(test1, action1, If(test2, action2, If(test3, action3))), shown below in a sequence of if/then/else pseudo-code statements: if (test1) action1 else if (test2) action2 else if (test3) action3 The IfElse() statement may be used to more cleanly express the flow of expression by removing the superfluous internal If() statements: IfElse(test1, action1, test2, action2, test3, action3) ifelse(test expression 1,instructions 1,test expression 2,instructions 2, ...) ifelse(isequal([media type], Audio), Le Tunes, isequal([media type], Video]), Flix) If media type is audio, outputs "Le Tunes", else if media type is video, outputs "Flix" ifelse(isequal([artist], Bob Dylan), Genius, isequal([album], Joshua Tree, 8), Great Album, 1, Mediocre) This example, implements the nested if statements from the If() section above, first testing if the artist is Bob Dylan, and if true, outputs "Genius", otherwise evaluates the second test to determine if the album is "Joshua Tree", and if true, outputs "Great Album", otherwise, performs a final test, in this case a degenerate test of 1 (and 1 is always true), thus outputting the value "Mediocre".

### Query, Test and Comparison Functions

All of the functions in this section, when used on their own, will only ever return one of two values, 1 (true) or 0 (false). There is a "FormatBoolean()" function that can be wrapped around these and allows us to specify the output for each case and is discussed in more depth in the Format section. The real power and versatility of these "Is" functions is released when they are wrapped inside the If() function discussed above.

#### Compare(...): Compares two numbers

 Compare() Compares two numbers, using the operators less than (<), greater than (>), or equal to (=). Outputs 1 if the comparison is true, and 0 otherwise. Available starting with MC17. compare(1st number, operator, 2nd number) Available Operators: =: numeric equivalence <: numeric less than <=: numeric less than or equal to >: numeric greater than >=: numeric greater than or equal to compare([bitrate], <, 320)If the 'bitrate' is less than 320 (Kbps), the output will be 1, otherwise, the output will be 0. If(Compare(Math(Now() - [Date Modified, 0]), >, 21), Expired, FormatDate([Date Modified, 0], Elapsed)) Shows the age of files under 21 days old, or shows 'Expired' for older files.

#### IsEqual(...): Compares two values in one of nine specified modes

 IsEqual() Compares two values in one of nine specified modes ("exact match", "Is greater than" etc.) and outputs 1 for a positive match and 0 for a negative match. If no compare mode is specified, the compare will default to 0. isequal(1st value to compare,2nd value to compare,compare mode) Available Compare Modes: 0: case-sensitive string compare for equality 1: case-insensitive string compare for equality 2: numeric compare for equality 3: numeric less than 4: numeric less than or equal to 5: numeric greater than 6: numeric greater than or equal to 7: substring search (case sensitive) 8: substring search (case insensitive) In all cases, the first value is always compared with the second value, never the other way around isequal([artist],[album],1)If the 'artist' and 'album' values are the same, the output will be 1, otherwise, the output will be 0. if(isequal([artist],[album],1),Self Titled,[album]) Wrapped inside an 'If' function, if the 'artist' and 'album' values are the same, the output will be 'Self Titled', otherwise, the output will be the 'album' value. if(isequal([artist],[album],1),Self Titled/,,[album]/)) This example demonstrates the character 'escaping' mentioned in the overview earlier. Here, we want the output to be either "Self Titled," (note the inclusion of the comma) or the album value with a closing parenthesis. In order to achieve this, the comma, and the closing parenthesis, are escaped using a preceding forward-slash character. This informs the expression evaluator that these characters are not part of the expression syntax and are to be treated literally if(isequal([filename (path)],Classical,8),Classical,Not Classical) Here, compare mode number eight has been specified, so, if the letters classical appear anywhere in the file path for a given file, the expression will return "Classical" and if not, it will return "Not Classical". Note that when using compare modes seven and eight, the subject must be given first, and the term to compare for given second

#### IsEmpty(...): Tests to see if a field is empty

 IsEmpty() Tests any given field for data. If the field is empty, the function returns 1, and if populated, the function returns 0. There are two different test modes available, a "string" test, and a "number" test. This is because as far as Media Center is concerned, fields designated as containing numerical values that are populated with the number zero, are empty. If no test mode is specified, the function will default to 0. Pay particular attention to the third example offered below, as it covers a caveat that comes with this particular function. isempty([field to test],test mode) Available test modes: 0: String test (field must be empty to get a positive result) 1: Numerical test (field must be empty, or contain 0 to get a positive result) isempty([comment],0)If the comment field is empty, this expression will return 1, but if the comment field contains data, the expression will return 0. isempty([track #],1) This expression will perform a numerical test for data in the [track #] field. If the field is empty, or contains 0, the expression will return a positive result, 1, otherwise, the result will be negative, 0. if(isempty([disc #]),,[disc #]) Here, by not entering any instructions to carry out for a positive result, the expression will do just that, and output nothing, but if the [disc #] field does contain data, the expression will write that out. Upon first look, you would think that this could work really well in the "Rename, Move, & Copy Files" tool for only creating a \Disc #\ directory if needed. This will not work. When asking the rename tool to create directories from field data, it is smart enough to know that directories with no name are illegal in Windows, so when it encounters an empty field, it automatically converts it to "Unknown [Field Name]". It does this before the expression engine gets to see it, which means that the IsEmpty function will always return a negative result when used in the rename tool, even when the specified field is indeed empty. As we now know that empty fields are passed through the rename tool as "Unknown [field name]" we can use if(isequal([disc #],unknown,8),,[disc #]) to achieve the desired result. Note that this only applies when using the rename files tool.

#### IsRange(...): Tests a value for inclusion within a given range

 IsRange() IsRange allows us to test if any given field falls inside any given range of values. If the field falls inside the given range, the function returns 1, and if outside the given range, the function returns 0. IsRange([Field to Test],Specified-Range) The range to test for can be letters or numbers, separated by a hyphen, without spaces, lowest value first, highest second. Letters and numbers cannot be mixed, the range can only be one or the other 1-100 a-z c-d 23-7542 isrange([artist],a-c)Abba or Blondie will return 1 (positive), and ZZ Top will return 0 (negative). if(isrange([bitrate],96-191),Poor Quality,High Quality) This expression will output "Poor Quality" for any file where the bitrate falls between 96 and 191, and "High Quality" for all others. Note that expressions are only as good as the instructions given, and that the above expression would label files with bitrates less than 96kbps as "High Quality". If this expression were used to add a category to a view, there would be two selectable choices in the category, Low Quality, and High Quality. Selecting either one would then filter the file list accordingly. This post on Interact shows the use of IsRange in a Search List. (right click the link, open in new tab to keep this page open). The expression format in that post shows how to form expressions for use in standard Media Center searches, something that was covered earlier on this page.

#### IsMissing(...): Tests to see if a file exists on the system

 IsMissing() This function tests the existence of a file in the file system. If the file is missing, the function returns 1 (positive), and if the file is found, the function returns 0 (negative). This function is useful for checking the integrity of your Media Center library as you can use it to produce a list of any files in your library that Media Center cannot find. Beginning with version 17, IsMissing() treats special entries such as ripped Blu-ray or DVDs as single files, even though they physically exist in the file system as several files and directories. Note: IsMissing() works directly on the file system and will cause performance to suffer: the larger the library, the longer it will take to produce results. IsMissing(Full Path To File) Checks for existence of the file "Full Path To File", or the current file if unspecified. ismissing()Checks if the current file exists, and returns 1 (positive) if the file does not exist, and 0 (negative) if the file does exist. ismissing(C:\Music\My Lost File.mp3) Checks for "My Lost File.mp3" and returns 1 (positive) if the file does not exist, and 0 (negative) if the file does exist. [=ismissing([filename])]=1 This example also demonstrates how to construct an expression for use as a Media Center search string. If you place this in the search field in the top right corner of the program while viewing all of your library, it will filter the list, leaving only the missing files on view. If your library is in good order, this list should be empty. You could also create a view scheme and use this string in the "Set rules for file display" search to give you a view that you can visit periodically to check that your library is intact if(ismissing(),File is missing,File exists) Wrapped inside an "If()" function, the expression outputs "File is missing" or "File Exists" depending on the result returned by IsMissing()

#### IsRemovable(...): Tests to see if a file is stored on removable media

 IsRemovable() Checks to see if a file resides on removable media and if so, returns 1 (positive), and if not, returns 0 (negative). There is not a lot to say about this function, especially since Media Center comes equipped with a [Removable] field by default that is automatically populated with 1 for all files in the library that are on removable storage. The function works in exactly the same way as the IsMissing function described above, returning 1 (positive) if the file is on removable storage, and 0 (negative) if not. IsRemovable(Full Path To File) If no file path is specified, the function will default to checking the current file. isremovable()Checks if the current file is on removable storage, and if so, returns 1 (positive), if not, the function returns 0 (negative).

#### IsInPlayingNow & IsPlaying(...): Tests to see if a file is in the Playing Now playlist or currently being played

 IsInPlayingNow() These two functions will be dealt with together as from their names, they are self-explanatory. One checks to see if a file has been added to the playing now list in any zone, and the other checks if a file in a list is currently playing or not, in any zone. With this in mind, their most practical use is as expression columns in a file list. To add an expression column to a list, right click on any existing column header and click on the "Add expression column" option. IsInPlayingNow()Checks the current file, and if in the Playing Now list, returns 1 (positive), and if not, returns 0 (negative). IsPlaying() Checks the current file, and if currently playing, returns 1 (positive), and if not, returns 0 (negative). if(isinplayingnow(),Selected,Not Selected)As mentioned in the description, the ideal place for these functions is as 'expression columns'. If this example were used in an expression column, then files added to Playing Now will show as "Selected" and all other files would show as "Not Selected". If the idea here is to be able to quickly see which files have been added, this might look a bit 'busy' and defeat the purpose, to which end, it is perfectly acceptable to tell the expression that if a file is not in Playing Now, to output nothing, by simply not giving any instructions for the negative result, like so: if(isinplayingnow(),Selected,). Now, this expression column will only show "Selected" against files that are in Playing Now, leaving all others empty, giving a much easier column to read. Use IsPlaying in exactly the same way as IsInPlayingNow() On the Interact support forum, mark_h describes how he puts these two functions to work for him, and rick.ca shows how he tweaked the idea when he answers the question: "is it possible to play an artist's full work when a genre is shuffling?"

### Formatting Functions

All of these functions (with the exception of FormatBoolean) take raw data from the library and allow us to present that data in a way that we choose. What does "raw data" mean? Media Center stores duration information in seconds and converts that information into hours (if needed), minutes and seconds for display in the Duration column in a file list. Likewise, file size information is stored in bytes and is converted into Mb for display in the file list. So there you have it, raw data. The following section gives some idea of what is possible using the raw data and the Format functions. To instruct the expression evaluator to use raw data, a zero is added to the library field, inside the square brackets, like so: [Date Imported,0]

#### Delimit(...): Outputs a value with head/tail strings when value is non-empty

 FormatNumber() Delimit() outputs a value if the value is non-empty, including head and/or tail strings. Nothing is output when the value is empty. Delimit(Value,Tail string,Head string) "Value" The value to be output if it is not empty. "Tail string" Optional, defaults to space. The string to append at the end of a non-empty Value. "Head string" Optional, defaults to empty. The string to append to the beginning of a non-empty Value. delimit([Track #], .) Appends a period (.) after a track number if [Track #] is not empty, e.g. "12.". delimit([Date (year)], {, }) Outputs the year surrounded by curly braces, e.g. "{2012}".

#### FormatBoolean(...): Formats a boolean (true / false) value in a specified manner

 FormatBoolean() This function is wrapped around another function and will return specified strings for true and false values returned by that other function. FormatBoolean(True/False Test,String to use if true,String to use if false) True/False Test Other functions perform their respective tests and return 1 to indicate a true result, and 0 to indicate a false result String to use if true,String to use if false If these are not specified, the function will default to using "True" and "False" formatboolean(isempty([number plays]),Never Played,Has Been Played)On it's own, the function isempty([number plays]) will return either 1 or 0. When wrapped inside a formatboolean function as shown here, the output for a true result will be "Never Played", and for a false result, the output will be "Has Been Played". formatboolean(isempty([number plays]))Here, there are no strings specified for the true/false results, therefore the function will default to using "True" and "False"

#### FormatDuration(...): Presents a duration of seconds in a reader friendly format

 FormatDuration() Media Center stores duration data in seconds, at up to sixteen decimal places. The value shown in the default "Duration" column in a file list is an internally formatted interpretation of this raw "Duration" data. As Media Center automatically applies this formatting for us, there is not a lot of call for this particular function. FormatDuration(Value to format) "Value to format" can be either the raw duration data, or a given number of seconds formatduration([duration,0])This expression will duplicate the contents of the default [duration] field as shown in a file list formatduration(600) This will output ten minutes in the format 10:00

#### FormatFileSize(...): Presents a number of bytes in a reader friendly format

 FormatFilesize() Media Center stores file size data internally in bytes. This function will convert those byte values into reader-friendly values, 3.2 Kb or 10.4 Mb, for example. The function will also accept a byte value directly. FormatFileSize(Value to format) "Value to format" can be either the raw [File Size] data or a given number of bytes. formatfilesize([file size,0])This expression will duplicate the contents of the default [file size] field as shown in a file list formatfilesize(56123456) This expression will convert 56,123,456 bytes and the output will be 53.5 MB

#### FormatNumber(...): Formats a number to a specified number of decimal places

 FormatNumber() FormatNumber() allows to format any given value to a set number of decimal places. FormatNumber(Value to format,Number of decimal places,Output if value is zero,Label if value is greater than 1,Label if value equals 1) "Value to format" This could be a library field, such as [replay gain] or the result of a Math() expression. Any numerical value you encounter where you would like to limit the number of decimal places displayed can have this function applied. "Number of decimal places" This is optional. If not specified, the function will default to zero decimal places. Use -1 to output as many decimal places as necessary. "Output if value is zero" This is optional. If not specified, the function will return zero. "Label if value is greater than 1" This is optional. If not specified, the function will not return anything, if specified, and the formatted number is greater than 1, the function will return with the number, plus this label. "Label if value equals 1" This is optional, as detailed below.. If not specified, but a label for greater than 1 has been specified, then this "greater than 1" label will always be used. If neither are specified, the function will not return anything. If both are specified, and the formatted number equals 1, the function will return with the number, plus this label. Note that even if you are only interested in applying a label for those results that equal 1, you must also indicate the preceding instructions, if only to instruct the evaluator to ignore them, as shown in the examples below. formatnumber([duration,0],2)This will return the duration of a track, in seconds, shown to two decimal places. formatnumber([number plays,0],0,Not played this one yet,Plays,Play) "0" decimal places has been specified, therefore the result will be a whole number with no decimals shown. If [number plays] is zero, the result will be "Not played this one yet" If [number plays] is greater than 1, lets say 6, the result will be "6 Plays" If [number plays] is 1, the result will be "1 Play" formatnumber([number plays,0],,,,Time) Here, the function will fall back to its defaults for everything except when the number equals one: No decimal places have been specified, the result will default to a whole number with no decimals shown. If [number plays] is zero, the result will be "0" If [number plays] is greater than 1, lets say 6, the result will be "6" If [number plays] is 1, the result will be "1 Time"

#### FormatRange(...): Formats a value as a range

 FormatRange() This function places any given value into its place in any given range. FormatRange(Value to format,Range size,Mode) Value to format: This could be a specific word or number, or any library field Range Size: A numerical value dependent on how you wish to set up your range. If not specified, this will default to 1 Mode: There are three possible modes, detailed below. If not specified, this will default to zero. 0: Automatically choose between number / letter grouping 1: Specifies that letter grouping should be used 2: Specifies that number grouping should be used formatrange([artist])This will return the first letter from the [artist] field. Note that as range size and mode values were not specified, the function defaulted to one and automatic respectively. formatrange([artist],3,1)This will take the first letter from the artist field and place it in the appropriate letter range. In this case, a range size of three has been specified, therefore the output will be in the form of "a-c", "d-f", "g-i" etc. etc. formatrange([bitrate],100,2)This will take the bitrate and place it in the appropriate number range. In this case a range of 100 has been specified, therefore the output will be in the form of "0-99", "100-199", "200-299" etc. etc. Note that this function always starts number ranges from zero, 0-9, 10-19, etc, etc.. If you really need a number grouping that starts from 1, 1-10, 11-20, 21-30,etc. etc., you can use expressions to create a pseudo range. Full details, with a helpful explanation, of "1 based grouping" can be found on this page.

### String Manipulation

The primary use of the functions in this section is to manipulate the data associated with any given file or files. When used with direct editing in the file list, or in the action window, as decribed here, they offer extremely fast and efficient methods for batch editing the actual tag data associated with multiple files.
Note that when used indirectly, in expression based columns, categories or library fields, the referred fields are not altered in any way, the data is merely presented in the expression field formatted as requested.

#### Clean(...): Returns a cleaned up version of a filled in template

 Clean() The Clean() function is used to generally strip empty bracketing, superfluous dash characters, leading or trailing articles, or replace filesystem-illegal characters. It is typically employed to clean the joining of several fields, some of which may be empty, or to produce filesystem-safe filenames. Clean(Value to clean, Mode) Value to clean: a string that will be cleaned Mode (optional, defaults to 0): 0: default clean, removes empty () and [], superfluous dash (-) characters and sometimes comma (be careful) 1: removes the article 'the' from the beginning and ', the' from the end 2: removes any article (a, an, the, etc.) from the beginning and end 3: replaces each filesystem-illegal character --- \ / : * ? " < > | --- with an underscore (_) Clean([Album] - [Date]) Consider the simple expression [Album] - [Date]. When the [Date] value is empty, the result will contain the undesirable dangling separator string " - " following the album name (e.g. "Greatest Hits - "). Using Clean() in the default mode removes this dangling string, and in this example produces "Greatest Hits". Clean(The Beatles, 1) For sorting or grouping purposes, it is often desirable to remove the leading article "The" from a string. Clean() in mode 1 provides a convenient solution, and in this example produces "Beatles". Clean(AC//DC: Back In Black, 3) When an expression is to be used to produce a filename, filesystem-illegal characters must be removed or converted to legal characters. Clean() in mode 3 will convert such characters into safe underscores. This example yields the filesystem-safe "AC_DC_ Back In Black". Note: the double forward slash is required above to produce a single double forward slash, since forward slash is the Media Center expression language escape character. Clean(\//:*?"<>|, 3) This trivial example demonstrates how all filesystem-illegal characters are converted to underscores, producing the nine-character string consisting entirely of underscores "_________".

#### FixCase(...): Changes the case of a given string

 FixCase() This function will output any given text string in one of five specified case modes. FixCase(String to modify,Case mode to apply)The "String to modify" can be plain text, a library field, or a combination of the two. The five modes available are: 0: Title Case 1: All Words 2: First word 3: ALL UPPERCASE 4: all lowercase If no case mode is specified, the function will default to using "Title Case". Title case will start each principal word with a capital. More detail regarding title case can be found here fixcase([album])This will take the contents of the [album] field and present it with the specified capitalisation. As there is no specified mode here, the function defaults to 0, so, if an album is entered in the library as "Time Out Of Mind", the function will return "Time Out of Mind" (note the lower case "of") fixcase(MY ALbUm IS cAlLeD [album],4)This would return "my album is called time out of mind"

#### FixSpacing(...): Intelligently splits adjacent camel-cased words

 FixSpacing() This FixSpacing() function inserts spaces between adjacent camel-cased words. For example, OneWorld becomes One World. This function is useful for helping to clean and convert metadata that favors compactness over standard sentence structure. FixSpacing(String to convert, Mode)The "String to convert" is any string of text. The available modes are: 0: Disables conversion 1: Enables camel-case conversion fixspacing([name], 1)Takes the contents of the [name] field and expands any camel-case into standard sentence structure. E.g. MiracleOn34thStreet becomes Miracle On 34th Street. fixspacing(Another [name], 1)Assuming the same [name] as above, this would return "Another Miracle On 34th Street".

#### Hexify(...): Hexifies a string to make it suitable for website usage

 Hexify() The only place this function is likely to be used is in the "Link Manager". Websites often don't like spaces in their addresses, and punctuation could confuse a site's search engine. Hexify attempts to take care of this by replacing spaces and punctuation with web friendly alternatives. For example, Bob Dylan would become Bob%20Dylan. Hexify(Value to hexify) hexify([artist] - [album])Oasis - (What's The Story) Morning Glory? becomes: Oasis%20-%20%28What%27s%20The%20Story%29%20Morning%20Glory%3F

#### Left(...): Retrieves a specified number of characters from the left of a value

 Left() This function retrieves a specified number of characters from the left of any given value. Left(Value to get characters from,Number of characters to get)"Value to get characters from" can be plain text, a library field, or combination of both. If more characters than exist are requested, all available characters are returned. left([filename],3)This will return the drive letter, colon and first back-slash from the filename. If asked to show more characters than actually exist, the expression will return the entire value, also, remember that spaces count as characters too.

#### Length(...): Returns the number of characters in a string

 Length() This function returns the number of characters in any given string. Length(String to count characters from)The "String to count characters from" can be plain text, a library field, or a combination of the two. length([filename])This will count the characters in the [filename] field and return the result. Spaces count as characters, so, C:\My File.mp3 would return 14. if(isequal(length([filename]),68,6),68 Characters or more,Less than 68 Characters)Here, Length() has been combined with another two functions, "If()" and "IsEqual()". The expression compares the length of the filename against the number 68. If there are 68 or more characters in the filename, the expression will return "68 Characters or more", otherwise, it will return "Less than 68 Characters". If you are working with a device with filename length limitations, these functions can be used to create extremely useful expressions that could help with your device management.

#### Mid(...): Retrieves specified characters from a value.

 Mid() Mid() retrieves a specified number of characters from a specified starting point in any given string. Mid(Value to get characters from,Character to start at,Number of characters to get) Value to get characters from: This can be a library field, plain text, or a combination of both. Character to start at: This is a numerical pointer, and rather confusingly, the function treats the first character as zero and begins from there. If not specified, the function will default to zero. Number of characters to get: If this value is not specified, the function will default to 1. -1 can be used to retrieve all available characters after the specified start point. mid(12345)As values for "Character to start at" and "Number of characters to get" have not been specified, they default to 0 and 1 respectively and the function returns the first character in the string, 1. mid(12345,1,2)The start point has been specified as the second character in, and 2 characters have been asked for, the result here will be 23. An example of Mid() being used to re-order a date field was given in answer to the question "Can I include seconds in "import date"?"

#### Regex(...): Regular expression pattern matching and capture

 Regex() This function performs regular expression (RE) pattern matching on its input. It can be used in one of three different modes: a test mode to test for a match, a capture output mode to output the specified captured pattern, and a silent, capture-only mode. All match captures are placed into special variables referenced as [R1], [R2], ... [R9], which can be used in subsequent expressions. The contents of the captures [R1] ... [R9] are available until the entire expression completes, or Regex() is run again, whereby they are replaced. The regular expression implementation used is the Microsoft 2010 TR1 engine. (Available since build 16.0.155.) Regex(String to test, Regular expression, Mode, Case sensitivity) String to test: One or more library fields, plain text, or a combination of both, which is used as the string evaluated for a match. Regular expression: This is the regular expression pattern used to perform matches and captures on the String to test.The regular expression language assigns special meaning to many characters. A few of these meta-characters, such as forward slash "/", comma "," and parenthesis "(" and ")", are also used by the Media Center expression language. To force the Media Center expression engine to ignore the meta-characters in regular expressions, surround the entire regular expression with /# and #/. This is Media Center's form of escapement, which tells the expression engine to ignore everything inside, so that the entire, uninterpreted regular expression can be provided to the Regex() regular expression evaluator. Although /# and #/ is not necessary when no conflicting characters are in use, and you may manually escape such characters with a forward slash "/", it is best practice to always encase a regular expression in /# and #/. Mode: Sets the mode in which Regex() will run. Optional, defaults to 0. 0: Runs in test mode, returning 1 or 0, indicating whether the string matched (1) or did not match (0) the pattern. This mode is useful within an if() test, so that different true (1) or false (0) actions may be taken. Output will be a 0 or 1. This mode is the default. 1 to 9: Outputs the specified Nth capture group's contents, where N ranges from 1 to 9. Currently, only a single capture is output in this mode, but all captures are available in the [R1] ... [R9] capture variables. This mode is used to easily output a single matching sub-string. -1: Runs in silent mode, with no output. This mode is useful as a means to capture portions of the string, and later use those captures in subsequent portions of an expression. Case sensitivity: Toggles the case-sensitivity of regular expressions. Optional, defaults to 0, ignoring case. To use this option, a value or comma-placeholder must also be set for the Mode option.Note: Case insensitivity does not apply to characters inside a character class [ ]. Use both uppercase and lowercase characters when necessary to match either case (e.g. [aAbB] to match either uppercase or lowercase A or B). 0: Ignore case when matching (e.g. the letters E and e are identical). This is the default. 1: Consider case when matching (e.g. the letters E and e are considered different). Example: Modes 1 through 9 The examples in this section use one of the modes from 1 through 9, to output the specified capture. Regex([Name], /#(Big.*Man)#/, 1) Matches track names that contain Big followed by Man, with anything (including nothing) in between, and outputs the matched tracks. Sample output: Big Butter and Egg Man Big Man Big Manager It's a Bigman Thing ‾‾‾‾ Regex([Artist], /#([(].+)$#/, 1) Matches against the Artist field and returns items that contain an opening (left) parenthesis followed by additional characters until the end of the artist string. Only the sub-string from any opening parenthesis until the end of the string will be returned, since this is the only captured portion. Sample output: (Brian Eno/U2) (feat. DJ Cam) (Otis Day & The Knights) (w/Emmylou Harris) ‾‾‾‾ Regex([Name], /#([(][^)]+)$#/, 1) Similar to the previous example, but matches track names that contain a opening (left) parenthesis, but are missing the closing (right) parentheses through the end of the track name. This might be useful to help detect tagging inconsistencies Sample output: (feat. David Bowie Examples: Mode 0 The examples in this section use mode 0, to test if a string does or does not match the pattern. The result of the test may be used to drive a conditional statement such as an if() statement. if(Regex([Artist],/#([[:punct:]])#/, 0),[R1] --> [Artist], No Punctuation) Matches against the Artist field looking for any punctuation character. The results of the Regex() expression will be a 0 (false) or 1 (true) since the mode is set to 0, The true side of the if() test is set to output the first (and only) capture, which is expressed as [R1], and is followed by the string " --> " and then the artist name. In the false case, the string "No Punctuation" is output. Sample output: "  --> Clarence "Frogman" Henry & --> Al Cohn & Zoot Sims .  --> Dr. John /  --> Bootsy Collins/Fatboy Slim ‾‾‾‾ if(Regex([Artist], /#([[:punct:]])#/, 0), Contains Punctuation\replace(replace([R1], ;,Semicolon), \, Backslash), No Punctuation)\replace(replace([Artist], ;, / and/ ), \, //)&DataType=[list] A more complex example, similar to the previous one. When used inside an expression column, builds an expandable tree with headings Contains Punctuation and No Punctuation that group artists based on whether or not their names contain any punctuation characters. Because semicolon and backslash are list separator characters for the expression language, for the example expression to work properly, these must be replaced (otherwise the list will not build as desired). In the list of punctuation, both backslash and semicolon characters have been replaced with their English equivalent words. In artist names, a semicolon is often used as a separator between the main artist and featured artists, so the expression replaces semicolons within an artist name with the word "and". Likewise, backslashes have been replaced with forward slashes. Sample output: ↓ Contains Punctuation ↓  $Payola$ ↓  *  D*Note → + → : → Backslash ↓  Semicolon  Lita Ford and Ozzy Osbourne  Seal and Jeff Beck → No Punctuation ‾‾‾‾ if(Regex([Album], /#^([^-]+[^\s])- (.*)$#/, 0), [R1]: [R2], / No Change Necessary) Some album names contain characters that are not legal in Windows, and after pulling properties from the file name, such characters will be translated into a dash "-" character (e.g. "Staring at the Sea: The Singles" becomes "Staring at the Sea- The Singles"). If you'd like to identify such possibly re-named album, an expression such the one above might help. The expression matches characters from the beginning of the line that do not contain a dash, followed by a non-space character, followed by a dash, space and everything else. Wrapped in an if() statement, these file names become apparent in an expression column. Examples: Mode -1 The examples in this section use mode -1, which cause Regex() to suppress output. This mode is only useful with captures, where the captures are utilized in subsequent portions of an expression. The previous example (which helped to identify album titles that may have been changed after tags were updated from file properties) used mode 0 to guide an if() evaluation. By using that expression column and selecting only the files whose album name should be changed, the identical Regex() statement can be used to easily fix the album property by changing the mode from 0 to -1: =Regex([Album], /#^([^-]+[^\s])- (.*)$#/, -1)[R1]: [R2] Editing the Album tag and pasting the expression above into the edit field will set the munged album name to use a colon rather than dash. Note: take care to select the correct files, and ensure the tags were changed as desired. Use Undo if not. A safety mechanism can be installed into the tag assignment. By using the same Regex() statement from the last mode 0 example, and setting the false side of the if() statement to [Album], the expression would effectively only change those files whose album names matched the pattern. Non-matched album names would be assigned to themselves, essentially acting as a no-op. For completeness, that statement would be: =if(Regex([Album], /#^([^-]+[^\s])- (.*)$#/, 0), [R1]: [R2], [Album]) ‾‾‾‾ Regex([Name], /#(\d{1,2})\.(\d{1,2}).(\d{4})#/, -1)[R3]//[R1]//[R2] Matches and captures a date formatted as dd.mm.yyyy anywhere within a filename, and rearranges it in a standard format of yyyy/mm/dd. Since Mode is set to -1, no output occurs. However, captured match segments are made available for subsequent use. The three captures, [R1], [R2] and [R3] are arranged in the textual output such that the year, month and day ordering are as desired. Sample output: 2011/08/19 2009/01/22 ‾‾‾‾ Regex([Name], /#^(.+?) $$([^(]+)$$$#/, -1)[R2]: [R1] This example shows how rearranging segments of track titles can help call out naming inconsistencies. The expression captures parenthetical information at the end of a track, and moves it to the beginning. In an expression column, inconsistencies become clearer. Sample output: Ext. Version: Blinded by the Light Extended Version: Peter Gunn extended version: the saftey dance feat. Crystal Lake: You Might Need Somebody Feat. Billy Godfrey: Look Around feat Amel Larrieux: Gaze ‾‾‾‾ listbuild(1, \, Regex([Name], /#^(.+?) $$([^(]+)$$\$#/, -1)[R2],[R1])&datatype=[list] Wrapping the previous expression in a listbuild() to create an expandable list provides quick grouping for even easier spotting of naming irregularities, especially when combined with Search to reduce the list size.

#### RemoveCharacters(...): Removes specified characters from a given field or string

 RemoveCharacters() This function will remove specified characters from a given field or string using one of three specified modes. (Available in build 16.0.148 onwards.) RemoveCharacters(String to test,CharactersToTestFor,Mode) String to test: This can be plain text, a library field, or a combination of the two. Characters to test for: series of characters, or strings of characters, placed all together between two commas, that are to be removed (note that this function is case sensitive) Mode: There are four available modes, each detailed below. Note that if no mode is specified, the function will default to using mode 0 (remove all instances) Available Modes: 0: Remove all instances 1: Remove from the beginning only 2: Remove from the end only 3: Remove from each end RemoveCharacters(Paper,Ppr,0)This will result in "ae" as P, p and r are removed. RemoveCharacters(Paper,Ppr,1)This will result in "aper" as "mode 1" has been specified, and the capital P is removed from the start. RemoveCharacters(Paper,Ppr,2)This will result in "Pape" as "mode 2" has been specified, and the lower case r is removed from the end. RemoveCharacters(Paper,Ppr,3)This will result in "ape" as "mode 3" has been specified, the capital P is removed from the start, and the lower case r is removed from the end. RemoveCharacters([artist],/(/),)This will remove any opening or closing brackets from anywhere within the [artist] field. Note how the brackets are 'escaped' as discussed in the 'Overview' section earlier.

#### RemoveLeft(...): Trims characters from the start of a value

 RemoveLeft() The output from this function will remove a specified number of characters from the start of any given value. RemoveLeft(Value to remove characters from,Number of characters to remove) removeleft([name],5)This would show the name field, with the first five characters removed. If asked to remove more characters than actually exist, the output will be blank, also, remember that spaces count as characters too..

#### RemoveRight(...): Trims characters from the end of a value

 RemoveRight() The output from this function will remove a specified number of characters from the end of any given value. RemoveRight(Value to remove characters from,Number of characters to remove) removeright([name],5)This would show the name field, with the last five characters removed. If asked to remove more characters than actually exist, the output will be blank, also, remember that spaces count as characters too..

#### Replace(...): Replace or remove strings from a value.

 Replace() Quite simply, this function allows to search for a specified string in a specified value, and if found, remove the specified string, or replace it with another. Replace(Value to check,String to check for,String to replace with) Value to check: This can be plain text, a library field, or combination of both. String to check for: Note that this check is case-sensitive String to replace with: Any instance of the "String to check for" will be replaced by this string. If not specified, any instance of the "String to check for" will be removed. replace(My Sample String,S,Replaced )All instances of upper-case "S" will be replaced by the text "Replaced ", (note the trailing space), resulting in "My Replaced ample Replaced tring" replace(My Sample String,s,Replaced )The "Value to check" does not contain any lower-case "s", resulting in unchanged output "My Sample String" replace(My Sample String,/ Sample,stic)In this example, the space preceding the word Sample is to be included in the "String to check for". Remembering that, as discussed in the Overview, spaces that follow a comma are ignored unless escaped, an escaping forward slash is used to force the inclusion of the space in the check. The result here will be "Mystic String".

#### Right(...): Retrieves a specified number of characters from the right of a value

 Right() This function retrieves a specified number of characters from the right of any given value. Right(Value to get characters from,Number of characters to get)"Value to get characters from" can be plain text, a library field, or combination of both. If more characters than exist are requested, all available characters are returned. right([filename],3)This will return the last three characters from the filename. If asked to show more characters than actually exist, the expression will return the entire value, also, remember that spaces count as characters too.

### List Manipulation

The default Media Center library contains many fields that are referred to as "list type" fields. Users are also able to add their own "list type" fields to their libraries. A list type field contains one or more text items seperated by semi-colons. The semi-colons are referred to as the 'delimiter' and when displayed in a view category, text items seperated by semi-colons are displayed in a list of seprately selectable items. The "Keywords" field is a classic example of a list type field, which demonstrates how list type fields allow a single file to be tagged with many different keywords, as opposed to a 'standard' field, such as 'Genre', where a single file can only be tagged with a single genre. The following functions provide the ability to combine or build custom list type fields using the default semi-colon delimiter, or a specified delimiter, count the number of items contained in a given list, or extract a numbered entry from within a list. Two of the functions listed in this section are used to create "list type" data from two or more existing sources and could reasonably be considered to be functions more suited to those who are very familiar with Media Center and how it gets its job done. If these functions are used to create a new 'calculated data' library field, they will not function as 'list type' fields unless the field is first created as a "User Data" field, with "List Type" specified. After creating the field in this way, it is possible to go back and edit the field, changing it to "calculated data" and entering an expression to be used. The "Eureka moment" occurred in November 2009.

#### ListBuild(...): Build a list from a series of values

 ListBuild() This function provides the ability to create a single list from many different sources and allows a list delimiter to be specified. It has two modes that can be applied and are detailed below. Of these two modes, mode "0" (Combine all values) should be avoided. It has been included for 'function completeness' only, and when used, can produce some very strange results that do not filter as expected. In order for the data generated by this function to be treated as list data, the 'datatype' must be specified as [list]. ListBuild(Mode,Delimiter,Items,To,Include) Mode: There are two different modes available: 0: combine all values. NOTE: This mode should be avoided as there is no recorded practical use for it, and it's behaviour can be unpredictable. 1: combine non-empty values Delimiter: The character used here will be used as a delimiter between each of the specified list items. To be clear, the keywords field uses a semi-colon delimiter by default; if a list is built using keywords and genre, and the specified delimiter is a back slash, it will be used between the keywords and genre fields when joining them, the semi-colons in the keywords field would not be altered. For example, if [keywords] contained "these;are;keywords" and [genre] contained "Rock", and these two were joined using ListBuild with a "\" specified as the delimiter, the resulting data would be "These;are;keywords\Rock". The real beauty and power of this function can be released when expressions are nested into the ListBuild instructions. For example, "listbuild(1,\,replace([keywords],;,\),[genre]" would return the data "These\are\keywords\Rock" Items To Include: This can be any number of specified text entries, expressions, or library fields, seperated by commas listbuild(1,;,[keywords],[genre])&datatype=[list]This will return a semi-colon delimited list containing all keywords and genres. If either keyords or genre is empty, they will be ignored, so, the data returned for a file with no keywords, and a genre of "Rock" would be simply "Rock". listbuild(1,\,[genre],[album artist (auto)],[album])&datatype=[list]When Media Center encounters a back slash character in a list type field, it 'nests' the data in the list. Think of this in exactly the same way as Windows reads file paths, each back slash is another folder along the file path, and in a Media Center list type view category, each back slash creates a virtual folder, and each semi-colon starts a new list entry, which means that effective browsing trees can be created using this knowledge. In the example shown here, a list of genres would be created, and each genre is able to be expanded to reveal a list of artists, which in turn can be expanded to reveal albums by that particular artist in that genre. So, now that this is getting interesting, there's an issue with this example. If a file has no specified [genre], the value is ignored, and the [album artist (auto)] value is placed on the root of the virtual tree, which means that the completely collapsed list contains a mixture of [genre] and [album artist (auto)]. The next example demonstrates how to clean that up. listbuild(1,\,if(isempty([genre]),!No Genre Applied,[genre]),[album artist (auto)],[album])&datatype=[list]Here, the previous example has been improved by nesting an IsEmpty() function into the listbuild function. The result is that all files without a specified genre are placed in a group at the top of the virtual tree called "!No Genre Applied", and the rest of the root consists of existing genre values, which is much tidier.

#### ListCombine(...): Combines two delimited lists into a single delimited list

 ListCombine() Unlike the ListBuild function above, which can be used to create a list from any number of varying sources, ListCombine() is used to merge two specified lists into one. In order for the data generated by this function to be treated as list data, the 'datatype' must be specified as [list]. ListCombine(First list,Second list,Input Delimiter,Output Delimiter) First List and Second List are specified library fields. Input Delimiter: This is the value that will be used to join the two specified lists. The value is optional, and if not specified, the function will default to using a semi-colon. Output Delimiter: This value is also optional. If specified, the function parses the output list (the result of the two lists, joined by the input delimiter) and replaces each occurrence of the input delimiter with the specified output delimiter. listcombine([people],[places])&datatype=[list]The result here would be a single, semi-colon delimited list containing all the values from the [people] and [places] fields. [people] contains Family\Mum;Family\Dad;Family\Gran [places] contains United Kingdom\Scotland\Edinburgh;United Kingdom\Scotland\Edinburgh\Edinburgh Castle The output list from the above expression would be: Family\Mum;Family\Dad;Family\Gran;United Kingdom\Scotland\Edinburgh;United Kingdom\Scotland\Edinburgh\Edinburgh Castle (the specified "listcombine delimiter" shown in bold and underlined) listcombine([people],[places],\)&datatype=[list]Here, the resulting list will be the [people] and [places] lists joined using a back slash. Remember that Media Center interprets back slashes as a folder hierarchy when displaying list type fields in a view category pane. [people] contains Family\Mum;Family\Dad;Family\Gran [places] contains United Kingdom\Scotland\Edinburgh;United Kingdom\Scotland\Edinburgh\Edinburgh Castle The output list from the above expression would be: Family\Mum;Family\Dad;Family\Gran\United Kingdom\Scotland\Edinburgh;United Kingdom\Scotland\Edinburgh\Edinburgh Castle (the specified "listcombine delimiter" shown in bold and underlined) listcombine([people],[places],\,;)&datatype=[list]Finally, a semi-colon output delimiter has been specified, therefore, all back slashes will be replaced by semi-colons, and the resulting list will be a single, flat list containing all the text entries from each field: [people] contains Family\Mum;Family\Dad;Family\Gran [places] contains United Kingdom\Scotland\Edinburgh;United Kingdom\Scotland\Edinburgh\Edinburgh Castle The output list from the above expression would be: Family;Mum;Family;Dad;Family;Gran;United Kingdom;Scotland;Edinburgh;United Kingdom;Scotland;Edinburgh;Edinburgh Castle (the specified "listcombine delimiter" shown in bold and underlined)

#### ListCount(...): Returns the number of items in a delimited list

 ListCount() ListCount is used to return the number of items that exist in any given field, using any given delimiter. ListCount([Field to count],Delimiter to use) Field to count: Typically, this will be a list type field, but this is not compulsory. The data in any field can be parsed using any chosen delimiter Delimiter to use: This is optional. If not specified, the function will default to using a semi-colon delimiter. Anything can be specified as a delimiter, from a single character to a whole word or words. listcount([People]) No delimiter has been specified here, therefore the function will default to using a semi-colon. The result here will match the number of people shown in a properly tagged photo. Note that the function is smart, so, if a file has no [People] tag, the function will return zero (0), and if it has [People] data, but no semi-colon, the function will return one (1). listcount([filename (path)],\) This function can be used to count the directories in a filepath by specifying a back slash as the delimiter. listcount([keywords],!People) This basic expression can be used as a building block to create a more complex expression to count the number of people tagged in a photo. the full expression can be seen here. That thread is actually the release thread for the 'new' nesting feature, introduced in 2007, and although 2 pages long, is worth a read as it contains some quite useful information.

#### ListItem(...): Returns a specified value from a delimited list

 ListItem() This function numbers list items starting from zero and returns the value of a specifically numbered item. ListItem([Field],Number of item to retrieve,Field delimiter to use) Field: The function will accept any given field, though is more typically used with list type fields. Number of item to retrieve: The number of the item in the list to retrieve. The list items are numbered starting from zero. Field delimiter to use: This is optional. If not specified, the function will default to using a semi-colon delimiter. Anything can be specified as a delimiter, from a single character to a whole word or words. listitem([filename],0,\)This function will return a file's drive letter plus colon. Note that the same result could be achieved by using left([filename],2), there is no 'right' or 'wrong' with these things, just personal preference, or 'what works for you'. A good rule of thumb is to use the simplest possible way to get to your goal, as less typing is better, and the more simple the expression, the easier it is to follow. listitem([filename],2,\)Here, the result will be the name of the second directory along a file's folder path from the drive root. C:\Folder1\Folder2\ are itemised as 0\1\2\, so rather confusingly, the second directory is actually the third item in the back slash delimited path. listitem([filename (path)],math(listcount([filename (path)],\)-1),\)This expression uses the math() and listcount() functions to find the "Number of item to retrieve" value. listcount() returns the total number of directories in the path, and the math function subtracts one from this number (because listcount() starts counting at one, but listitem starts counting from zero), this number is then used by the listitem function. The result will be the name of the parent folder of each file. Setting the expression up in this way means that the result will always be reliable regardless of the number of folders in the filepath as the expression will work all of this out for itself.

### Date & Time Functions

Media Center provides several functions for date and time conversion, formatting and generation. Internally, date and time for date fields is stored as a floating point number, where the integer portion represents the number of days since the Epoch, and the decimal portion represents the fraction of a day.

The Windows locale setting will affect the interpretation and formatting of date and time information.

#### ConvertDate(...): Converts a human-readable date to the internal format required for use in date fields

 ConvertDate() Converts human-readable date / time strings into the floating point representation used internally by Media Center to represent date and time. convertdate(Date string) Date string A human-readable date string to be converted. convertdate(3/6/2012)Converts the date March 6th, 2012 into a floating point number that can be assigned to a date field. formatdate(convertdate(12/2/1985), decade)) Converts the date string December 2nd, 1985 into internal date/time form, and then formats the result as a decades grouping of "1980's". This might be used for grouping tracks by decades.

#### FormatDate(...): Formats a date value in a specified manner

FormatDate() FormatDate provides custom formatting of date / time fields through the use of special format specifiers. Select from the available format specifiers, and arrange them to produce the desired date and time components.
Construction formatdate(Date value, Format string, Output if date is empty)
• Date value The date to be formatted, in Media Center internal format (i.e. a floating point value). This field is optional, and will default to [Date,0]. To use any date field, use the raw (unformatted) field specification (e.g. [Date Imported,0]).
• Format string The format specifier string to format the date or time components. Media Center supports Windows style, strftime() style, and Media Center-specific specifiers. Select from any of the format specifiers in the following table. See also: [1]
• Output if date is empty If the provided date is empty, anything placed here will be output instead. This could be plain text, such as "No Date", or a library field. This value is optional, and if not given, the expression will default to return nothing if the date is empty.
Examples formatdate(year-month)
Returns the file's date formatted as Year-Month. This uses the default [Date,0] field. Example: 2012-April.

formatdate([last played,0],yyyy//MM//dd,Not Yet)
This will return the last played date as year/month/day without the time, and regardless of the system locale setting. If a file has no last played info, the expression will output "Not Yet" instead.

formatdate([date modified,0], month %Y)
This will return the month and 4-digit year a file was modified. Example: December 2010.

formatdate([date imported,0],month)&datatype=[month]
If you were to use the previous expression to create a view category that contained the months your files were imported, it would list the months alphabetically, with April first and September last. Thankfully, we can specify "data types" for expressions which further fine tune how Media Center displays the results. In this case, a data type of month has been specified, therefore Media Center will list the months in the correct chronological order. Data types were discussed earlier on this page.

#### Now(...): Retrieve and display the system date

 Now() Now() will return the raw system date. "raw" data is discussed in the Field description, and also in the introduction to the "Format" functions. As Media Center's raw date data is illegible, this function needs to be used with the "FormatDate()" function, which allows the current date, and time, if desired, to be presented in many different styles. Now() formatdate(now(),date)Returns the current date, without the time, formatted according to the system settings on which the function is running. formatdate(now(),dddd dd MMMM yyyy) padnumber(formatdate(now(),hour),2):padnumber(formatdate(now(),minute),2) Here, three seperate expressions have been strung together to return a fully formatted current date and time: Sunday 26 September 2010 14:04 [=isequal(formatdate([date imported,0],MM//yyyy),formatdate(now(),MM//yyyy)]=1 ~sort=[Date Imported]-d Media Center comes with a stock smartlist titled "Imported This Month". On the face of it, this could be a handy list of files, but is actually rather misleading. Closer inspection of this stock smartlist reveals that it is not actually listing files "Imported This Month", but instead, listing those files that have been imported in the past 31 days by using the following rule: [Date Imported]=<31d ~sort=[Date Imported]-d This would mean that if you were to view that list on the second of March, you could potentially be looking at a list of files imported during three different months. The example in bold above corrects this anomaly by comparing the month/year imported with the current month/year, and only lists the file if the two match. This is also an example of how to use an expression in a search rule, as detailed in "When, Where and How to use expressions" This topic expands on the example above a little by showing how to construct rules that return files that have been played or imported today or yesterday.

### Other Functions

The functions in this group are varied, and do not readily fit into the other groups of functions.

#### Counter(...): Counts upwards in specified increments

 Counter() This function can be used to number objects sequentially, from a specified starting point, in specified increments. The counter resets itself to zero after five seconds of inactivity.Counter() can exhibit a touch of wierdness when used in certain situations, which will be covered in the examples, that demonstrate why this one is not really a 'fits all' function. Counter(Number to start counting from,Increments to count up in) Number to start counting from: This is optional. If not specified, the counter will start from one. If specified, the start value is inclusive, meaning that if a start value of five is specified, the first value the function returns will be five. Increments to count up in: This optional. If not specified, the counter will count up in increments of 1 counter()This shows the function in its simplest form. The counter will start at one and count upwards in increments of 1. padnumber(counter(370,2),4)This expression shows a combined use of functions. Counter() will count up, in two's, starting from 370, and the padnumber function will pad the results to four figures, giving output values of 0370, 0372, 0374, etc. etc.. WeirdnessCounter() works really really well, and really really efficiently when used to sequentially number static data fields. It is not designed to be used in a dynamically changing expression column in a file list. To demonstrate this, right click on a list column header and choose the option to "Add expression column". Use the first, simple expression above, and press OK. The column is presented and all the items in the list are now numbered in this column, but, see what happens when you run the cursor up and down the list? The counter function just keeps on going and going. Right click on the expression column header, and it will appear at the top of the selectable columns list with a tick beside it, click on it to remove the column. This same anomally appears when counter() is used in the "Rename, Move, & Copy Files" tool. There may be a possible solution to this effect as seen in the renaming tool by using the CustomData(#) function, but only if the count is to start from 1.Some interesting reading regarding the use of Counter() can be found in answer to "how to fill the NAME field with incrementing numbers?" and "Prepending a consecutive number to titles as I copy them from MC13 to mp3 player".

#### CustomData(...): Sequence numbering when renaming files

 CustomData() The official description for this function goes as follows: "Returns custom data stored in a file array (used primarily for internal uses)." There is no recorded practical use for this function, with the exception of using it with a hash symbol in the library tool called "Rename, Move, & Copy Files". When used in the directory or filename rules of this tool, this function will number the files in the list from first to last, starting at number one. As long as any desired numbering is to begin at one, this function is a reasonable alternative to combat the wierdness demonstrated by the Counter() function, and could be particularly useful when renaming image files. If the numbering is required to start counting from anywhere other than one, then Counter() will need to be used, taking the wierdness and its work arounds into account. CustomData(#) padnumber(customdata(#),4)_Christmas Party 2007It's important to remember that this function will only work when used as part of the renaming rule for either filename or directory (or both) within the "Rename, Move, & Copy Files" tool. In this example, imagine 324 photos from the Christmas party of 2007 were selected for renaming, and this expression was entered into the filename field. The resulting filenames would be 0001_Christmas Party 2007.jpg through to 0324_Christmas Party 2007.jpg. Note how the "padnumber()" function has been used to add the leading zeros.

#### FileName(...): Returns the name from a specified file name

 FileName() This function returns the file name for the files in a list, or for the specified file. A second parameter set to 0 will cause the suffix to be suppressed from the file name. The library field [Filename (Name)] already contains the value that would be returned by FileName(); it generally should be used rather than this function. FileName(Filename to check, Suppress suffix) Filename to check This is optional. If not specified, the function defaults to the current file. Suppress suffix This is optional. If set to 0, the file name's suffix will be suppressed from output. filename(C:\Music\File.mp3)The result here would be... "File.mp3" filename(C:\Music\File 2.wav, 0)The result here would be... "File 2" filename()Returns the file name for each file in the list. The [filename (Name)] field returns the same information.

#### FileFolder(...): Returns the name of a parent sub-folder from a specified file path

 FileFolder() This function returns a parent sub-folder name from a file path. A value of Unassigned will be returned when the specified level exceeds the root of the path. FileFolder(Filepath, Level) Filepath This is optional. If not specified, the function defaults to the path of the current file. Otherwise, the specified path will be used. Level This is optional. Specifies the parent sub-folder name to return, working the path from right-to-left (i.e. bottom of the folder tree upwards to the top). A value of 0 (the default) specifies a file's immediate parent, 1 its grandparent, etc., up to the root of the path. filefolder()filefolder([Filename,0], 0)Returns the name of the file's parent folder. filefolder(c:\some\path\to\a\file.ape, 2)filefolder(c:\some\path\to\a\, 2)Returns the great grandparent sub-folder name "path". Notice above that the file name is not required in the path. FileFolder() works by looking from the end of the file path until it finds a backslash (\).

#### Math(...): Evaluates a given mathematical formula

Math() The Math() function provides the ability to perform mathematical calculations. In addition to the standard arithmetic operators, it also supports various numerical, trigonometric, and comparative functions. Simple variables are supported, as are multiple statements.
 Arithmetic Operators + Addition - Subtraction * Multiplication / Division ^ Power % Modulo Boolean Operators ! NOT & AND | OR Grouping Operators ( ) Precedence grouping Comparison Operators } Absolute value maximum (i.e. x or y that is maximum distance from 0). { Absolute value minimum (i.e. x or y that is minimum distance from 0). > Distance between x and y, positive when x greater than y, negative otherwise. < Distance between x and y, positive when x less than y, negative otherwise. Functions abs(x) Returns the absolute value of x. sign(x) Returns the sign of x (1 when x >= 0, -1 when x < 0). log(x) Returns the natural logarithm (base e) of x. log10(x) Returns the common logarithm (base 10) of x. pow(x,y) Returns x raised to the y-th power. rand(x) Returns a random value ranging between 0 to x. randn(x) Returns a random value ranging between -x and x. Comparison Functions min(x,y) Returns the minimum value of x and y. max(x,y) Returns the maximum value of x and y. equal(x,y) Returns 1 when x = y, 0 otherwise. below(x,y) Returns 1 when x < y, 0 otherwise. above(x,y) Returns 1 when x > y, 0 otherwise. Trigonometric Functions atan(x) Returns the arctangent of x. cos(x) Returns the cosine of x. sin(x) Returns the sine of x. tan(x) Returns the tangent of x. abscos(x) Returns the absolute value of cosine(x). abssin(x) Returns the absolute value of sin(x).

The order or precedence of the operators is summarized as follows, from top to bottom:

 (  ) ! ^ *  / Left to right +  - Left to right |  & Left to right

Variables may be assigned and used by specifying a simple string of letters. Examples: math(val=2) or math(x=pow(2,3))

Multiple equations may be specified, each separated by a semicolon. Expressions are evaluated left to right. The final value of the Math() function will be the result of the right-most equation. Example: math(x=4; pow(2^x))

Note: Fields used inside of Math() are expanded directly. Those that have no value (eg. empty fields) may produce incomplete Math() statements. For example, if the field [Number Plays] is empty, an expression such as math([Number Plays] + 2) would be seen by Math() as " + 2". This incomplete expression would by an error. See this topic for additional explanations and workarounds.

Please also note: The Math() function uses dot (.) as the decimal point, so Math(1,5+1,5) will not work but Math(1.5+1.5) will. If you run MC on a system that uses comma (,) as the decimal point, all date related fields - [Date,0], [Last Played,0], [Date Modified,0], [Date Imported,0] etc. - with time information will in their raw format use comma as the decimal point. This is also the case with the Now() function. In these cases you must replace the commas with dots for the Math() function to work, like this: Math(Replace(Now(),/,,.) - Replace([Last Played,0],/,,.)). The escape character / must be used to have the commas recognised as commas.

Construction Math(Expression to evaluate)
Examples math(10 + 4)
Returns 14.

math(10 + 2 * 25)
Returns 60, demonstrating that multiplication has higher precedence than addition.

math((10 + 2) * 25)
Returns 300, demonstrating that parenthesis grouping has higher precedence than multiplication.

listitem([filename (path)], math(listcount([filename (path)], \) - 1), \)
Evaluates the ListCount() function to determine the number of path components in the field [filename (path)], and uses Math() to subtract one. The result is then used in the ListItem() function which yields the parent folder name of the specified file.

#### Note(...): Retrieve information from a note

 Note() Since build 14.0.111, Media Center has shipped with a "Notes" feature. One of the many uses available via notes is the ability to store contact information, and that information can be labelled. Labels are typical contact information labels such as "Home phone", "Work phone", "Email" etc. etc.. This function can retrieve and display the contents of specified labels from a note. Note(Field Label,Field Type,Occurrance) Field Label: There are too many labels to list here. To see the available labels, select some text in a note and right click that selected text, then hover the cursor over "Set Field" to see the list of available labels. Field Type: If the specified label was, for example, "Phone", then the "Type" could be "Home" or "Business" or any of the other available "Phone" types. This value is optional, and if not specified, the function will default to the first type encountered. Occurrance: If a note contained two home phone numbers, they would be "occurrance 0" and "occurrance 1". If "occurrance 1" was required, the function requires this to be specified. This value is optional, and if not specified, the function will default to using zero. note(phone)note(phone,home)note(phone,home,1)Here are three sample notes expressions. In the image below, they have been used to create expression list columns, with each expression used shown in the column header. The note, with labels on show, is visible on the right hand end of the image. When comparing the note with the data returned by each expression, it should become apparent how each expression is working. A note + expression columns (click to enlarge)

#### Orientation(...): Outputs the orientation of an image

 Orientation() Outputs a word indicating the orientation of an image file. Orientation() Portrait: Output when an image's height is greater than its width. Landscape: Output when an image's width is greater than its height. Portrait: Output when an image's height is equal to its width. if(isequal(orientation(), Square), Square, Rectangle) Outputs Square for square images or Rectangle for portrait and landscape images.

#### Tag(...): Returns a physical file tag (rather than looking in the database)

 Tag() This function originally came into being as a need arose for there to be a way to re-import the exif date information from image files without affecting any other tags. To that end, the function works well, but that's really where it's functionality ends. Success with any other fields has been extremely limited indeed. The main reason for this is because, when using this function to query specific tag data blocks in an image file, the fields referenced by the tag() function must be spelled exactly as they appear in the tag block within the file, and yes, they are case sensitive. It is also extremely important to know that when building a file list that contains a "Tag()" derived column, Media Center will be inordinately slower, 1000's of times slower, in building that list than it would be without the "Tag()" column. This is because each and every file in the list must be queried individually for the contents of the specified tag. This particular function is best used using the "inline editing" method outlined in the "When, Where and How to use expressions" section of this page, to pull the desired data into the main library database and then reference the information from the database. Tag(Field to read from the file)Specific tag data blocks from jpg files can also be referenced:Tag(Tag Block To Query: Field to read from the tag block) Field to read from the file: Not case sensitive in all scenarios, but always case sensitive when targeting specific tag data blocks within jpg files. Tag blocks that can be queried from within jpg files are: EXIF XMP IPTC MJMD tag(artist)This will return the artist information from a file if that file contains the artist tag tag(Gapless Header) or tag(Gapless Footer)These two expressions allow gapless information to be queried from mp3 files. tag(exif: Date)This will return the raw date data from the EXIF data saved inside a jpg file. If this expression is used to import the data into Media Center's default [Date] field, Media Center will format the info into legible date information automatically. If importing into a custom field, wrap the tag() function inside a FormatDate() function like so: formatdate(tag(exif: Date),datetime).Note that "tag(exif: date)" will not return any result as the tag to query value is case sensitive and must be entered as "Date"

#### TVInfo(...): Returns television-specific information about a file

 TVInfo() Used to retieve and display specified televison information for a file. TVInfo(Information to retrieve) Information to retrieve: The options available for use here are: IsProgram: Tests whether the file is a program or not. (Returns 0 or 1) IsGuideProgram: Tests whether the file is a guide program or not. (Returns 0 or 1) IsRecordedProgram: Tests whether the file is a recorded program or not. (Returns 0 or 1) Channel: Returns the channel name, given a channel number. ChannelKeywords: Returns channel keywords. NameDisplay: Returns the name. NameDisplayWithDate: Returns the name + date. SeriesDisplay: Returns the series name. TimeDisplay: Shows the start time of a program using the system time format, but uses "Showing" if the program is on now. TimeDisplayNoOnNow: Shows the start time of a program using the system time format, without special handling for programs on now SizeDisplay: Returns the duration, formatted nicely for a television program. WatchedDisplay: Watched information, like no, yes, 80%, etc. TVInfo(namedisplay)Click on "Tools > Options > Theater View", then click on "Customize file info panel", then choose "Television Program" from the drop-list at the top. It is then possible to use this function to tailor the information displayed on screen in Theater view when looking at TV programs. Some of the default items already utilise this function offering real world, real time examples of their usage. TV programs use the field "Date Recorded" to store the program time. The "Date" field is the original air / production date.

#### Watched(...): Outputs a formatted bookmark position within a video

 Orientation() Outputs a video's bookmark position in a human-readable format. Watched() 0: Output a human-readable watched status. 1: Output a numeric watched value, 0 if not watched, 1 if partially watched, 2 if entirely watched. 2: Output a watched checkmark if watched Watched() Outputs formatted watched status, such as, 57% on Sep 25, or Aug 21, or nothing when the video has not been watched.

### Redundant Functions?

Taken at face value, all of the functions in this section would appear to be a little on the redundant side, falling neatly into the "a long way for a shortcut" category. Media Center could possibly rely on these functions internally, exalting their status to "highly useful" or "essential" even, but as this page is designed for end users, not Media Center, end users will find these functions redundant, and they are included here in the name of completeness only.

#### Field(...): Returns the value of a library field

 Field() Place the name of any library field inside this function, and it will return the contents of that library field for each file. Entering the field name inside square brackets as normal, without the function, returns the same data. Note: Beginning with version 17, Media Center no longer supports function expansion inside the Field() parameter list; only simple text strings are supported. This is a performance optimization. Field(Field name to retrieve) field(duration)Returns the formatted duration value for each file. field(duration,0) would return the raw duration data. Simply entering [duration] or [duration,0] returns the same result.

#### FilePath(...): Returns the path from a specified filename

 FilePath() This function will return the file path information from root to parent folder for all files in a list, or for any specified file. Media Center has a [Filename (Path)] library field by default, which is probably easier to use or reference than this function. FilePath(Filename to check) Filename to check This is optional. If not specified, the function defaults to the current file. filepath(C:\Music\File.mp3)The result here would be... "C:\Music" filepath()Returns the filepath for each file in the list. The [filename (path)] field returns the same information.

#### FileVolume(...): Returns the volume name from a specified filename

 FileVolume() This function will return the volume name information for all files in a list, or for any specified file. Media Center has a [Volume Name] library field by default, which is probably easier to use or reference than this function. FileVolume(Filename to check) Filename to check This is optional. If not specified, the function defaults to the current file. filevolume(C:\Music\File.mp3)The result here would be... "C:" filevolume()Returns the file name for each file in the list. The [Volume Name] field returns the same information.

#### AlbumKey(...): Returns a unique album key for a file

 AlbumKey() Testing reveals that this function simply returns an "[album artist (auto)] - [album]" string for each file. If two different albums happen to have the same [album artist (auto)] and [album] data, their respective AlbumKey() will not be unique. AlbumKey() AlbumKey()Create a new expression column in a list using this function and the result will be a column populated with the [album artist (auto)] - [album] data for each file.

#### AlbumArtist(...): Returns the calculated album artist for a file

 AlbumArtist() This function simply returns the "[album artist (auto)]" data for each file. AlbumArtist() AlbumArtist()Create a new expression column in a list using this function and the result will be a column populated with the [album artist (auto)] data for each file.

#### AlbumType(...): Returns the album type for a file

 AlbumType() This function simply returns the "[album type]" for each file. [album type] is a default Media Center library field that informs the user of an album's status in the library, such as "Single artist (complete)" or "Multiple artists (incomplete)" AlbumType() AlbumType()Create a new expression column in a list using this function and the result will be a column populated with the [album type] data for each file. The [album type] library field will work just as well, and return the same information.

#### Size(...): Returns the size of a file in a media type independent manner

 Size() Dependent on media type, this function returns the following information: Audio: Duration Video: Duration Image: Dimensions Data: No information returned. Size() Size()Create a new expression column in a list using this function and the result will be a column populated with media type dependent data for each file as listed in the function description above.

#### TrackNumber(...): Returns the track # of a file

 TrackNumber() This function simply returns the track # of a file. If a file has no track # assigned, the function returns zero.This function has no real use and is actually flagged as "For internal use only", so, not one for end users, and again, only included here for the sake of completeness. TrackNumber() TrackNumber()Create a new expression column in a list using this function and the result will be a column populated with the track # information for each file.