#!/bin/bash

# killall--Sends the specified signal to all processes that match a 
#   specific process name.

# By default it only kills processes owned by the same user, unless
#   you're root. Use -s SIGNAL to specify a signal to send to the process, 
#   -u USER to specify the user, -t TTY to specify a tty, 
#   and -n to only report what should be done, rather than doing it.

signal="-INT"      # Default signal is an interrupt.
user=""   tty=""   donothing=0

while getopts "s:u:t:n" opt; do
  case "$opt" in
        # Note the trick below: the actual 'kill' command wants -SIGNAL 
        #   but we want SIGNAL, so we'll just prepend the '-' below.
    s ) signal="-$OPTARG";              ;;
    u ) if [ ! -z "$tty" ] ; then
           # Logic error: you can't specify a user and a tty device
           echo "$0: error: -u and -t are mutually exclusive." >&2
           exit 1
         fi
         user=$OPTARG;                  ;;
    t ) if [ ! -z "$user" ] ; then
           echo "$0: error: -u and -t are mutually exclusive." >&2
           exit 1
         fi
         tty=$2;                        ;;
    n ) donothing=1;                    ;;
    ? ) echo "Usage: $0 [-s signal] [-u user|-t tty] [-n] pattern" >&2
        exit 1
  esac
done

# Done with processing all the starting flags with getopts...
shift $(( $OPTIND - 1 ))

# If the user doesn't specify any starting arguments (earlier test is for -?)
if [ $# -eq 0 ] ; then
  echo "Usage: $0 [-s signal] [-u user|-t tty] [-n] pattern" >&2
  exit 1
fi

# Now we need to generate a list of matching process IDs, either based on 
#   the specified tty device, the specified user, or the current user.

if [ ! -z "$tty" ] ; then
  pids=$(ps cu -t $tty | awk "/ $1$/ { print \$2 }")
elif [ ! -z "$user" ] ; then
  pids=$(ps cu -U $user | awk "/ $1$/ { print \$2 }")
else
  pids=$(ps cu -U ${USER:-LOGNAME} | awk "/ $1$/ { print \$2 }")
fi

# No matches? That was easy!
if [ -z "$pids" ] ; then
  echo "$0: no processes match pattern $1" >&2; exit 1
fi

for pid in $pids
do
  # Sending signal $signal to process id $pid: kill might still complain
  #   if the process has finished, the user doesn't have permission to kill
  #   the specific process, etc., but that's okay. Our job, at least, is done.
  if [ $donothing -eq 1 ] ; then
    echo "kill $signal $pid"   # the –n flag: "show me, but don't do it"
  else
    kill $signal $pid
  fi
done

exit 0