Execute command when grep finds a match-CodePudding

I have a program that continuously runs and is piped into grep and every once in a while grep finds a match. I want my bash script to execute when grep finds the match.

Like this:

program | grep "pattern"

grep outputs -> script.sh executes

CodePudding user response：

Use -q grep parameter and && syntax, like this:

program | grep -q "pattern" && sh script.sh

where:

-q: Runs in quiet mode but exit immediately with zero status if any match is found

&&: is used to chain commands together, such that the next command is run if and only if the preceding command exited without errors (or, more accurately, exits with a return code of 0). Explained here.

sh script.sh: Will run only if "pattern" is found

CodePudding user response：

Equivalent to @masterguru's answer, but perhaps more understandable:

if program | grep -q "pattern"
then
    # execute command here
fi

grep returns a zero exit status when it finds a match, so it can be used as a conditional in if.