how to use awk with echo in bash

Question

If i run in bash script (similar to this one) to send content to a file:

sudo ./bar.sh > foo

content bar.sh:

echo 'for pid in $(ps -ef | grep "smbd" | awk '{print $2}'); do kill -9 $pid &> /dev/null; done'

foo out:

for pid in $(ps -ef | grep "smbd" | awk {print }); do kill -9 $pid &> /dev/null; done

$2 is lost in out.

expected output:

for pid in $(ps -ef | grep "smbd" | awk '{print $2}'); do kill -9 $pid &> /dev/null; done

How do I get it?

Answer 1

First of all, never run things with sudo unless it is actually necessary to run them with sudo. I really cannot emphasize that enough. Unless you get a "permission denied" error, you don't need sudo and you should not use sudo. So you don't need sudo ./bar.sh, just run ./bar.sh.

Next, you don't need to echo to get the results of a command. This isn't needed:

echo '$(ps -ef | grep "smbd" | awk '{print $2}')'

All you need is to run the command itself. You don't need the command substitution ($(command)) or the echo. Just have this in your script:

ps -ef | grep "smbd" | awk '{print $2}'

Note that if you want to get the PID of a running process, you don't really want ps either. You can just use pgrep smbd which avoids the problem of the grep process itself appearing in the results.

Finally, if you want to print a multi-line string as output, you can use a here doc instead of many echo statements. So, putting all that together, you should make bar.sh like this:

#!/bin/sh
cat <<'EoF'
for pid in $(ps -ef | grep "smbd" | awk '{print $2}'); do 
    kill -9 "$pid" &> /dev/null
done
EoF

And then run it as ./bar.sh > foo (no sudo!).

Or, here's a simpler version of the same approach:

#!/bin/sh
cat <<'EoF'
ps -ef | awk '/smbd/{print $2}' | while read pid; do 
    kill -9 "$pid" &> /dev/null
done
EoF

Or, even simpler:

#!/bin/sh
printf '%s\n' 'kill -9 $(pgrep smbd)'

Which brings us to the final point of are you sure you really want a script for this? To kill all running smbd processes, all you need is a single command:

pkill -9 smbd