Shell snippet for automating cron script registration at boot

[PaulC]

Here's a little snippet of shell script, intended to go into the services-start script in /jffs/scripts. It scans the USB drive for files having a .cron extension, and for each of those it finds, scans for a comment line containing 'cron:' and uses what follows to register that schedule using cru.

This isn't going to impress the accomplished, but maybe it'll help others.

#
# look for cron scripts on the USB drive, and register them with cru
#
basedir=$(nvram get apps_mounted_path)

if [ -d "${basedir}" ]
then
    for file in $(find "${basedir}" -name '*.cron')
    do
         id=$(basename "${file}" .cron)
         schedule=$(sed -n -e '/^#[ \t]*cron:/ {s/^#[ \t]*cron:[ \t]*\(.*\)$/\1/;p}' "${file}")
         cru a "${id}" "${schedule} ${file}"
    done
fi

Here's a simple example: my 'backup-settings.cron' script that backs up my router's settings onto my thumb drive daily:

#!/bin/sh
# cron: 07 4 * * * 
#
dir=$(dirname "$0")

nvram show > "$dir/settings/nvram-show.txt"
nvram save "$dir/settings/nvram-dump.bin"
cp -a /jffs "$dir/settings/"

Note for the security conscious: it's a very bad idea to run scripts automatically from removable media. If your router isn't in a physically secure location, please don't use this technique, or add some signature to .cron files that's unique to your router (that an attacker won't know), and check for it.