[Chapter 40] 40.15 crontab Script Makes crontab Editing Easier/Safer

40.15 crontab Script Makes crontab Editing Easier/Safer

I've made mistakes with the crontab command, accidentally deleting my crontab file and not being able to get it back. I like the SunOS crontab -e command for interactive editing. So, I made a shell script that does it. To help keep me from using the system version, I store this script in a directory near the start of my PATH (8.7 ) ; if I really need the system version, I type its absolute pathname.














umask
 


trap
 
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${..-..}
 
cmp

#! /bin/sh
cmd=/usr/bin/crontab    # THE SYSTEM VERSION

# MAKE SURE EVERYONE KNOWS WHAT THEY'RE RUNNING:
echo "Running Jerry's crontab command..." 1>&2

case $# in
1)  ;;  # OK
*)  echo "Usage: `/bin/basename $0` -e | -l | -d"; exit 1 ;;
esac

case "$1" in
-[ld]) $cmd $1 ;;   # EXIT WITH STATUS OF REAL COMMAND
-e) # EDIT IT:
    umask 077
    stat=1  # DEFAULT EXIT STATUS; RESET TO 0 FOR NORMAL EXIT
    start=/tmp/CRONTAB$$s   end=/tmp/CRONTAB$$e
    trap 'rm -f $start $end; exit $stat' 0 1 2 15
    $cmd -l > $start || exit    # GET COPY OF CRONTAB
    /bin/cp $start $end
    ${VISUAL-${EDITOR-vi}} $end
    if cmp -s $start $end
    then echo "The crontab file was not changed." 1>&2; exit
    else
        $cmd $end
        stat=$? # EXIT WITH STATUS FROM REAL crontab COMMAND
        exit
    fi
    ;;
*)  echo "Usage: `/bin/basename $0` -e | -l | -d"; exit 1;;
esac

- JP