Song ratings with playlists in cmus

gistfile1.sh

#!/bin/bash
# Usage: cmus-rate [1-5]
#
# Rate tracks playing in cmus and add them to corresponding playlists.
#
# The track currently playing in cmus is added to an M3U playlist corresponding
# to the given rating ("[1-5].m3u") and removed from any other rating playlist.
# If no argument is given, the track is removed from all rating playlists.
#
# The playlists are kept sorted.

# Path to playlists
playlists="$HOME/music"

# Prefix and suffix strings for playlist filenames
pl_prefix=''
pl_suffix='.m3u'

# Get currently playing track from cmus
track=$(cmus-remote -Q | grep file)

# Errors
# + Inaccessible playlist directory
if [ ! -d "$playlists" ]; then
    mkdir -p "$playlists"
    if [ ! -d "$playlists" ]; then
        notify-send 'cmus-rate' 'Rating failed: Failed to create playlist directory.'
        exit 1
    fi
fi
# + No track playing
if [ -z "$track" ]; then
    notify-send 'cmus-rate' 'Rating failed: No track is currently playing.'
    exit 1
fi
# + Incorrect argument given
if [ -n "$1" ] && { [ "$1" -lt 1 ] || [ "$1" -gt 5 ]; }; then
    notify-send 'cmus-rate' "Rating failed: Incorrect argument given ($1)."
    exit 1
else
    rating="$1"
fi

# Path to lock file
lock='/tmp/cmus-rate.lock'

# Lock the file (other atomic alternatives would be "ln" or "mkdir")
exec 9>"$lock"
if ! flock -n 9; then
    notify-send 'cmus-rate' 'Rating failed: Another instance is running.'
    exit 1
fi

# Strip "file " from cmus output
track=${track/file \///}

# Temporary file for grepping and sorting
tmp="$playlists/tmp.m3u"

# Remove track from all rating playlists
for n in {1..5}; do
    f="$playlists/${pl_prefix}$n${pl_suffix}"
    if [ -f "$f" ] && [[ $(grep -q "$track" "$f") -eq 0 ]]; then
        grep -vF "$track" "$f" > "$tmp"
        mv -f "$tmp" "$f"
    fi
done

# Append track to new rating playlist
if [ -n "$rating" ]; then
    f="$playlists/${pl_prefix}$rating${pl_suffix}"
    printf '#EXTM3U\n%s' "$track" >> "$f"
    sort -u "$f" -o "$tmp"
    mv -f "$tmp" "$f"
fi

# The lock file will be unlocked when the script ends

Does the script actually work? See cmus/cmus#1066 (comment)

@sebw The script has been working for years. (I have made some minor changes in a new revision.)

I made some changes to create relative playlists
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