No command executed after performing kill command in shell script - shell

Question

Here is my shell script:
#!/bin/bash
PIDS=$(ps -e | grep $1 |grep -v grep| awk '{print $1}')
kill -s SIGINT $PIDS
echo "Done sendings signal"
I am passing the name of the process as command line argument.
The echo command is not getting executed, although the target processes are actually receiving the SIGINT signal and exited.
Any suggestions?
Update:
I changed the code to:
#!/bin/bash
PIDS=$(ps -e |grep $1 | grep -v grep | awk '{print $1}'|grep -v $$)
echo $PIDS
kill -s SIGINT $PIDS
echo "Done sendings signal"
echo "The current process is $$"
Now I am noticing a strange thing:
The script is working but not as expected. Executing following command in command line outside the script
ps -e|grep process-name|grep -v grep|awk '{print $1}'|grep -v $$
gives pid of the process-name but when I execute the same command inside shell script, assign it to variable PIDS and then echo PIDS then it shows one more pid in addition to the pid of process-name. Therefore when the kill command executes it gives an error that the process with second pid doesn't exist. It does echo the remaining sentences in the terminal. Any clue ?

Answer 1

There really are only a couple of possibilities. Assuming you're just running this from the command line, you should see the message ... unless, of course, what you're doing puts the PID of your shell process in PIDS, in which case the kill would kill the (sub) shell running your command before you hit the echo.
Suggestion: echo $PIDS before you call kill and see what's there. In fact, I'd be tempted to comment out the kill and try the command, just to see what happens.
#!/bin/bash
PIDS=$(ps -e | grep $1 |grep -v grep| awk '{print $1}')
echo $PIDS
# kill -s SIGINT $PIDS
echo "Done sendings signal"
Of course, you can always run the script with bash -x to see everything.

Answer 2

Your script works. The only reason I can see for the echo not being executed is that some value of $1 and the script file name combine so that your script PID is also gathered, thereby making the script suicide.
The PIDS line spawns a process running ps, grep, another grep -- so you won't find in PIDS the processes running grep, but what about the parent process itself?
Try:
#!/bin/bash
PIDS=$(ps -e | grep $1 |grep -v grep | awk '{print $1}' | grep -v "^$$\$" )
kill -s SIGINT $PIDS
echo "Done sendings signal"
or run the pipes one after the other with suitable safety greps.
Edit: it is evident that the "$1" selection is selecting too much. So I'd rewrite the script like this:
#!/bin/bash
# Gather the output of "ps -e". This will also gather the PIDs of this
# process and of ps process and its subshell.
PSS=$( ps -e )
# Extract PIDs, excluding this one PID and excluding a process called "ps".
# Don't need to expunge 'grep' since no grep was running when getting PSS.
PIDS=$( echo "$PSS" | grep -v "\<ps\>" | grep "$1" | awk '{print $1}' | grep -v "^$$\$" )
if [ -n "$PIDS" ]; then
kill -s SIGINT $PIDS
else
echo "No process found matching $1"
fi
echo "Done sending signal."

Answer 3

ps -e is identical to ps -A and selects all processes ( cf. http://linux.die.net/man/1/ps ), i. e. ps -e displays "information about other users' processes, including those without controlling terminals" (Mac OS X man page of ps). This means you will also kill the PID ($$) of your shell process, as already pointed out by Charlie Martin, because you will also grep a line of output of the ps -e command that looks like so:
67988 ttys000 0:00.00 /bin/bash ./killpids sleep
Just log the output of ps -e to a file to see that your script commits suicide:
./killpids sleep 2>err.log
#!/bin/bash
# cat killpids
echo $$
for n in {1..10}; do
sleep 5000 &
done
sleep 1
unset PIDS
PIDS="$(ps -e | tee /dev/stderr | grep "$1" | grep -v grep | awk '{print $1}')"
#PIDS="$(ps -www -U $USER -o pid,uid,comm | tee /dev/stderr | grep "$1" | grep -v grep | awk '{print $1}')"
wc -l <<<"$PIDS"
#kill -s SIGINT $PIDS
echo kill -s TERM $PIDS
kill -s TERM $PIDS
echo "Done sendings signal"