Count the number of processes and kill them - bash

Question

I am writing a script to kill all instances of the same process. As it is going to be used on Linux, AIX, HP-UX and Solaris, I need to use only built-in bash (sh) functions. That's why killall, pkill, etc. don't work for me.
Once there is only one instance of a process it should be just killed in traditional way:
kill -TERM `ps -ef | grep -v grep | grep $process | awk '{print $2}'`
However sometimes the program has extra instances running and that's why ps -ef | … returns more than one PID. That needs to be reported.
example:
bash-3.2$ ps -ef | grep -v grep | grep perl | awk '{print $2}'
5267
5268
5269
5270
5271
My thought was to store those values in a temporary variable and then send kill signal to each in a for loop.
bash-3.2$ tmp=`ps -ef | grep -v grep | grep perl | awk '{print $2}'`
bash-3.2$ echo $tmp
5267 5268 5269 5270 5271
However I still need the information if such a case occurred (how many instances were present).
It seems I need to check the whole string stored in the tmp variable and maybe count spaces?
Anyway the questions reduces to how to check how many values the $tmp variable stores?

Answer 1

For maximum portability and reliability, use -A (POSIX synonym of -e) and a custom format with -o rather than -f.
Your filtering of the output of ps is brittle: it may match other processes. You've had to exclude the grep process, and you may need to exclude your script as well, and there may be other completely innocent processes caught in the fray (such as your script itself) because their command line happens to contain $process as a substring. Make your filtering as strict as possible. With ps -o pid= -o comm=, you get just two columns (PID and command without arguments) with no header.
You don't need to use a loop to do the killing, kill accepts multiple arguments. For the counting, let the shell do it: you have a whitespace-separated list of numbers, to let the shell do the word splitting (with $(…) outside quotes) and count the number of resulting words ($#).
count_and_kill_processes () {
set -- $(ps -A -o pid= -o comm= |
awk -v "name=$process" '$2 == name {print $1}')
count=$#
if [ $# -ne 0 ]; then kill "$#"; fi
}
count_and_kill_processes foo
# now the number of killed processes is in $count
If your shell is bash or ksh on all machines, you can use an array.
pids=($(ps -A -o pid= -o comm= |
awk -v "name=$process" '$2 == name {print $1}') )
if [[ $# -ne 0 ]]; then kill "$#"; fi
# the number of killed processes is ${#pids}

Answer 2

use xargs:
ps aux | grep -ie perl | awk '{print $2}' | xargs kill -9

Answer 3

You can use a loop which should work in both cases:
for pid in $(ps -ef | grep -v grep | grep $process | awk '{print $2}'); do
echo $pid
done
Or count the number of matches:
if [ $(ps -ef | grep -v grep | grep $process | awk '{print $2}' | wc -l) -gt 1 ]
then
# more than one
fi