Thread: Combine if and grep

Hello, nixcraft forums!

Is there a way to combine if and grep, so that if executes a command if grep finds a matching string in a file? If yes, can you show me the syntax?

grep command return exit status 0 if match found if not then exit status 1
you can use grep and if
ex.

HTML Code:

#!/bin/bash
read -p "Please enter Username to check user exist or not:- " USERNAME
grep $USERNAME /etc/passwd 2>&1 >/dev/null
if [ $? -eq 0 ]; then
echo "$USERNAME available on this system"
else
echo "$USERNAME not found "
fi

Thank you!

hi,

to be precise

Code:

#!/bin/bash

read -p "Please enter Username to check user exist or not:- " USERNAME
grep -q $USERNAME /etc/passwd >/dev/null 2>&1 && echo "$USERNAME available on this system" || echo "$USERNAME not found "

theses simple tests don't need if statements.
beware, redirection has to be this, not rahul's; see bash man page about redirections.

Hi Watael,

beware, redirection has to be this, not rahul's; see bash man page about redirections.

but why this also works "/etc/passwd 2>&1 >/dev/null"

Originally posted by Watael
don't need if statements.

we knew it we can use "&& ||"
but Numbad Question related to combine if and grep
thats the reason i post that code.

I understand. sometimes I do it too

Hi Watael,

Thanks for correcting me
i am wrong , i checked all scripts under "/etc/init.d/" , in all scripts i found this code ">/dev/null 2>&1"