Собссно сабж. Зову из custom actions
/bin/bash -c "for f in %F; do convert $f /tmp/f.jpg && mv /tmp/f.jpg ${f\%\.*}.jpg; done"
/bin/sh: for f in '/home/picts/shot0083.png'; do convert $f /tmp/f.jpg && mv /tmp/f.jpg ${f\.*}.jpg; done: bad substitution
/bin/bash -c "for f in %F"'; do convert $f /tmp/f.jpg && mv /tmp/f.jpg ${f\%\.*}.jpg; done'
thunar-volman: Unsupported USB device type.
thunar-volman: Unsupported USB device type.
thunar-volman: Unsupported USB device type.
thunar-volman: Unsupported USB device type.
thunar-volman: Unsupported USB device type.
thunar-volman: Unknown block device type.
thunar-volman: Unknown block device type.
/bin/bash: ${f\.*}.jpg: bad substitution
inb4 затолкай в отдельный скрипт — не хочу его волочить.