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