grep command doesn't work when run remotely

Question

I have a script like this:

if rsh $server grep "string" /usr/path/file.txt
then
   echo "yes"
else
   echo "no"
fi

Basically I want to check the file in remote server containing some specific strings. It doesn't work and always display "yes" whatever I put into "string".

However, if I remove "rsh $server", which means running locally, and put that file into local, it is working fine.

Does anyone know what the problem is? How can I modify my script?

are you sure you're testing the grep exit code, and not rsh's? — Marc B, Jul 28 '15 at 20:49
The exit status of `rsh` is just whether you were able to connect successfully, it doesn't transmit the exit status of the remote command. — Barmar, Jul 28 '15 at 20:49
Can you use `ssh` instead of `rsh`? It wil do what you want. — Barmar, Jul 28 '15 at 20:52
Found this wrapper for `rsh` that gets the remote exit status: https://gist.github.com/schlomo/7908037 — Barmar, Jul 28 '15 at 20:53
@Barmar But it is working for rsh if I run the following command: rsh $server ps -fuctc | grep xxx | grep -v grep >/dev/null — user2597504, Jul 28 '15 at 21:00
That's because you're running `ps` remotely, but running `grep` locally. — Barmar, Jul 28 '15 at 21:02
@Barmar Thanks a lot. I try: rsh $server cat /usr/path/file.txt | grep "string" and it seems like working. — user2597504, Jul 28 '15 at 21:08

score 2 · Accepted Answer · answered Jul 28 '15 at 21:04

2

You can run grep locally with data from the remote file:

if rsh $server cat /usr/path/file.txt | grep "string"
then
    echo "yes"
else
    echo "no"
fi

This will be slow if the file is large, since the entire file has to be sent over the network so that the local grep can read it.

answered Jul 28 '15 at 21:04

Barmar

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lol thank you very much. I just replied you and we are both find this solution at the same time I think :) – user2597504 Jul 28 '15 at 21:09
It was your `ps` example that gave me the idea for this. – Barmar Jul 28 '15 at 21:13

grep command doesn't work when run remotely

1 Answers1