Shell Scripting: Expert Recipes for Linux, Bash, and More

logger

logger is a command-line tool that uses the syslog facility present on most Unix and Linux systems. This has a few benefits, one of which is that it allows a non-privileged shell script to write to log files owned by the superuser. It also means that the actual file that gets written to is determined by the system administrator, not the author of the script. This provides additional flexibility and customization.

$ cat checkfs.sh
#!/bin/bash
logger -t checkfs -p user.info "Starting checkfs"
df | cut -c52- | grep -v "Use%" | while read usage filesystem
do
  if [ "${usage%\%}" -gt "85" ]; then
    logger -t checkfs -s -p user.warn "Filesystem $filesystem is at $usage"
  fi
done
logger -t checkfs -p user.info "Finished checkfs"

checkfs.sh

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda5              28G   27G  395M  99% /
tmpfs                 1.5G     0  1.5G   0% /lib/init/rw
udev                  1.5G  248K  1.5G   1% /dev
tmpfs                 1.5G     0  1.5G   0% /dev/shm
/dev/sda3              56G   55G  1.8G  97% /iso
/dev/sda6             134G  124G  3.3G  98% /home/steve
$ ./checkfs.sh
checkfs: Filesystem / is at 99%
checkfs: Filesystem /iso is at 97%
checkfs: Filesystem /home/steve is at 98%
$

This results in the following log messages being added to the /var/log/messages file. Notice that although the script was run as an unprivileged ...