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.TH PLAYLISTFS 7
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.SH NAME
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playlistfs \- playlist file system
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.SH SYNOPSIS
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.B games/playlistfs
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[
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.B \-s
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.I postname
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]
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[
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.B \-m
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.I mountpoint
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]
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[
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.B \-a
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]
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.SH DESCRIPTION
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.B Playlistfs
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implements an audio player which plays files from a built-in play list.
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The player is controlled through three files, usually mounted at
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.BR /mnt .
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The files are
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.B /playctl
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for controlling play: start, stop, pause, skip, etc.;
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.B /playvol
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for controlling the playout volume; and
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.B /playlist
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for controlling the play list itself.
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.PP
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All three files can be written to control the player and read to obtain player
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status information.
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.PP
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When read, the files report the current status of the player, volume and playlist,
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respectively.  End of file is indicated by a read that returns zero bytes, as usual.
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However, in all three files, subsequent read operations will block until the status
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of the file changes and then report the changed state.  When the changed state has
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been read, another end-of-file indication is given, after which another read
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can be issued to wait for state changes.
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.PP
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The
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.B /playctl
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file returns strings of the form `\f2cmd n\fP'
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where
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.I cmd
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is one of
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.IR stop ,
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.IR pause ,
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or
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.I play
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and
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.I n
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is an index (or offset) into the playlist; indices start at zero.
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.PP
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The commands that can be written to
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.B /playctl
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take the same form; however, the index is an optional argument.  If the
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index is omitted, the current value is used. The commands are
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.IR play ,
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.IR stop ,
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.IR pause ,
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.IR resume ,
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and
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.IR skip .
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.I Play
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starts playing at the index.
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.I Stop
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stops playing.  If an index is given, the current index is set to it and
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can be used in future commands.
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.I Pause
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and
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.I Resume
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interrupt and continue play, respectively.  The index argument is always ignored and
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the whole command is ignored if the state in which they occur does not
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make sense.
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.I Skip
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adds the argument to the current index (adds one if no argument is given)
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and starts play at that index, stopping current play, if necessary.
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.PP
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Reads of
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.B /playvol
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return strings of the form
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.BR "`volume \f2n\fP'" ,
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where
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.I n
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is a number or, if there is more than one channel, a quoted set of numbers, between 0
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(minimum) and 100 (maximum).
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Writes to
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.B /playvol
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take the same form.
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.PP
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The
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.B /playlist
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file is an append-only file which accepts lines with one or two fields
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per line (parsed using
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.BR tokenize ).
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The first, compulsory, field is a file name, the optional second argument
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may contain a reference to, or a description of, the item, for instance in a graphical
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user interface.
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.B /playlist
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is append-only, individual lines cannot be removed.  However, the playlist
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can be cleared by opening the file with the
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.B OTRUNC
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flag.  A process that has
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.B /playlist
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open while the file is truncated will receive an error on the next read with
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.B errstr
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set to
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.IR "reading past eof" .
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When this error occurs, clients can seek to the beginning of the file and reread its contents.
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.PP
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After starting up,
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.B Playlistfs
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puts itself in the background. When called with the
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.B \-s
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flag, it posts a mountable file descriptor in
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.BR /srv/playlist.\f2postname\fP .
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The
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.B \-m
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flag can be used to specify a mount point other than
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.BR /mnt .
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.PP
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The files to be played are recognized by one of four extensions, and an appropriate
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player is then selected to play them.  Files without a recognized extension are played by the
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.I pac
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player:
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.TP
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\&.mp3
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/bin/games/mp3dec
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.TP
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\&.pac
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/bin/games/pac4dec
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.TP
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\&.pcm
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/bin/cp
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.TP
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\&.ogg
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/bin/games/vorbisdec
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.SH FILES
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.BR /srv/playlistfs.\f2user\fP :
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default
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.B playlistfs
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mountable file descriptor used by juke(7).
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.br
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.BR /mnt/playctl :
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Control file
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.br
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.BR /mnt/playlist :
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Playlist file
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.br
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.BR /mnt/playvol :
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Volume control file
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.SH SOURCE
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.B /sys/src/games/music/playlistfs
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.SH SEE ALSO
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.IR juke (7),
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.IR audio (7)