Quod Libet allows you to rename files based on their :ref:`tags<AudioTags>`. In some cases you may wish to alter the filename depending on whether some tags are present or missing, in addition to their values.
Quod Libet allows _pattern_ syntax for this interaction, as well as plain text. A pattern is some text surrounded by angle brackets, typically containing tags.
A common pattern might be:
<tracknumber>. <title~version>
You can use a | to only insert text when a tag is present:
<tracknumber|<tracknumber>. ><title~version>
You could also specify literal text to use if the tag is missing by adding another |:
<album|<album>|No Album> - <title>
A reasonable use of albumartist would be:
<albumartist|<albumartist>|<artist|<artist>|No artist>>
..which uses the first of the following: Albumartist, Artist or "No artist".
You can also move (rename) files across your filesystem to another
directory by mixing path elements and <pattern> syntax:
/home/*username*/Music/<artist>/<album>/...
Like tagging by filename, renaming by tags uses tag names enclosed by
<...> to substitute values. To rename songs as their artist followed
by their title, use <artist> - <title> (The file extension, .ogg, .mpc,
and so on, is automatically added). Other common patterns include
<tracknumber>. <title><tracknumber>. <artist> - <title>~/music/<artist> - <album>/<tracknumber>. <title>~/music/<artist>/<album>/<tracknumber>. <title>
You can also use tied tags to rename, e.g. <artist~title>.
Note that if you use / (a directory separator) in your filename, you
''must'' start the pattern with a / (or a ~/, which expands to your
home directory). To see why, consider what would happen if you tried to
rename the same file twice with <artist>/<title>. The first time it
would go under Artist/Title.ogg, the second time,
Artist/Artist/Title.ogg. When you specify the full path, this can't
happen.
If you don't use a / in the pattern, the file gets put in the same directory.
Consider the <tracknumber>. <title> pattern.
When the file is missing a track number, you get a filename that starts with ., which isn't good. So Quod Libet lets you use ''conditional renaming'' to avoid that.
To use conditional text, after the tag name (but inside the <...>) put
a | (a pipe). Then after the pipe, place all the text you want,
including other tag names inside <...>. That text will only be added when
that tag isn't empty.
To avoid the original problem, only display the track number, period, and space when the track number tag exists:
<tracknumber|<tracknumber>. ><title>.
Quod Libet also lets you change the text if a tag ''doesn't'' exist: Use a
second pipe. <tracknumber|<tracknumber>|00>. <title> will use the
track number at the start of the filename if it exists, or 00 if it
doesn't.
Remember that the format for conditionals is
<condition|<conditional tag>|<else tag>>.
You can also embed conditions inside each other:
/mnt/musik/<genre|<genre>/><artist|<artist>|Unknown>/<album|<album>/><tracknumber|<tracknumber> - ><title>
Let's dissect this:
/mnt/musik: A music partition<genre|<genre>/>: If there is a "genre" value, put the song into that folder (creating the folder if necessary). If there is no tag genre, skip this level in the folder hierarchy (note that the trailing slash of<genre>/is inside the < > that delineate the conditional "block".<artist>|<artist>|Unknown>/: If there's a tag artist, put everything into that folder, else put into a folder called "Unknown". Note that the trailing slash is outside the < > that delineate the conditional block, since we always want that folder level.<album|<album>/>: Album folder as needed, else skip<tracknumber|<tracknumber> - >: Prepend tracknumber if it exists<title>: The track title (or empty string)
For songs that don't have a genre tag, perhaps we'd want to use the "language" tag and sort into that folder instead. But many songs would have a genre and language tag values, and those songs should only go into the genre folder (i.e. the language folder should be ignored)
QL can do this, by expanding the <genre> conditional
block from the expression above to <genre|<genre>/|<language|<language>/>>.
The pipe after the second <genre>/ introduces what should be
done if the first condition isn't met (i.e. no genre tag),
but here instead of putting plain text,
we introduce a second conditional block, <language|<language/>>,
which adds a language tag folder, if the song has a tag "language".
The full expression now looks like this:
/mnt/musik/<genre|<genre>/|<language|<language>/>><artist|<artist>|Unknown>/<album|<album>/><tracknumber|<tracknumber> - ><title>