38.13 Interactively Kill Processes Matching a Pattern

When you want to kill processes, it's a pain in the neck to run ps (38.5 ) , figure out the process ID, and then kill the process. The zap shell script was presented by Brian Kernighan and Rob Pike in their classic book The UNIX Programming Environment . The script uses egrep (27.5 ) to pick the processes to kill; you can type extended expressions that match more than one process, such as:

% zap 'troff|fmat'


   PID TTY TIME CMD
 22117  01 0:02 fmat somefile? n


 22126  01 0:15 sqtroff -ms somefile? y

We've reprinted the script by permission of the authors:

`...`
 

#! /bin/sh
# zap pattern:  kill all processes matching pattern

PATH=/bin:/usr/bin
IFS='
'                   # just a newline
case $1 in
"")   echo 'Usage: zap [-2] pattern' 1>&2; exit 1 ;;
-*)   SIG=$1; shift
esac

echo '   PID TTY TIME CMD'
kill $SIG `pick \`ps -ag | egrep "$*"\` | awk '{print $1}'`

The ps -ag command displays all processes on the system. Leave off the a to get just your processes. Your version of ps may need different options (38.5 ) .

This shell version of zap calls another script, pick , shown below. [6] pick shows each of its command-line arguments and waits for you to type y , q , or anything else. Answering y writes the line to standard output, answering q aborts pick without showing more lines, and any other answer shows the next input line without printing the current one. zap uses awk (33.11 ) to print the first argument (the process ID number) from any ps line you've selected with pick . The inner set of nested (45.31 ) backquotes (9.16 ) in zap pass pick the output of ps , filtered through egrep . Because the zap script has set the IFS variable (35.21 ) to just a newline, pick gets and displays each line of ps output as a single argument. The outer set of backquotes passes kill (38.10 ) the output of pick , filtered through awk .

[6] The MH mail system also has a command named pick . If you use MH, you could rename this script to something like choose .

If you're interested in shell programming and that explanation wasn't detailed enough, take a careful look at the scripts - they're really worth studying. (This book's shell programming chapters, 44 through 46, may help, too.) Here's the pick script:

-n
 /dev/tty
 





done <
 

#!/bin/sh
# pick:  select arguments

PATH=/bin:/usr/bin

for i
do
    echo -n "$i? " >/dev/tty
    read response
    case $response in
    y*)    echo $i ;;
    q*)    break
    esac
done </dev/tty