term% cat index.txt PLAYLISTFS(7) Miscellaneous Information Manual 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. However, 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; how‐
ever, 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 fu‐
ture commands. Pause and Resume interrupt and continue play, respec‐
tively. 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 neces‐
sary.
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 (maximum). 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 tokenize). The first, compulsory,
field is a file name, the optional second argument may contain a refer‐
ence to, or a description of, the item, for instance in a graphical
user interface. /playlist is append-only, individual lines cannot 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 be‐
ginning 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 extensions, and an
appropriate player is then selected to play them. Files without a rec‐
ognized extension are played by the pac player:
.mp3 /bin/games/mp3dec
.pac /bin/games/pac4dec
.pcm /bin/cp
.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)
PLAYLISTFS(7)