#!/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.

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

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

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

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

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

# No matches? That was easy!
if test -z $pids  {
  echo "$0: no processes match pattern $1" > !2; exit 1
}

for pid in [$pids]
{
  # 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 test $donothing -eq 1  {
    echo "kill $signal $pid"   # the –n flag: "show me, but don't do it"
  } else {
    kill $signal $pid
  }
}

exit 0