CODEWITHSUNDEEP
bashif-statementgrepstdout
Francois B
Francois B

Reputation: 483

Bash conditional 'OR' of grep results

I am trying to do a conditional check of the result of two grep commands in a bash script, but I cannot seem to combine them like:

if [[ $( stout_cmd1 | grep -q 'check_txt1' ) || ( $( stdout_cmd2 | grep -q 'check_txt2' ) ]] ; then
    //do something here if output of stdout_cmdX contains text check_txtX
fi

as it always returns false. Conditionally checking the commands on their own work as intended:

if stdout_cmd1 | grep -q 'check_txt1' ; then

or 

if stdout_cmd2 | grep -q 'check_txt2' ; then

I don't know how to check if either one is true. How does one combine two stdout outputs in a conditional check? I have removed the -q flag from the grep calls with no effect.

Upvotes: 2

Views: 1689

Answers (2)

Inian
Inian

Reputation: 85845

Actually you just use the exit-code of grep directly after asking it to run silent -q

if cmd1 | grep -q "check_txt1" || cmd2 | grep -q "check_txt2"
then
    echo "Your code here!"
fi

Upvotes: 3

Toby Speight
Toby Speight

Reputation: 30933

The [[ compound command evaluates a conditional expression, but you just want the result of a pipeline. You need to combine your two pipelines in a list using ||:

if stout_cmd1 | grep -q 'check_txt1' || stdout_cmd2 | grep -q 'check_txt2'
then
    # your code here
fi

From the Bash manual:

A list is a sequence of one or more pipelines separated by one of the operators ;, &, &&, or ||, and optionally terminated by one of ;, &, or <newline>.
...
The return status of AND and OR lists is the exit status of the last command executed in the list.

Demonstration

#!/bin/sh

for i in 00 01 02 12
do
    if echo "$i" | grep -q '1' || echo "$i" | grep -q '2'
    then
        echo "$i contains a 1 or 2"
    else
        echo "$i contains neither 1 nor 2"
    fi
done

This produces the following output:

00 contains neither 1 nor 2
01 contains a 1 or 2
02 contains a 1 or 2
12 contains a 1 or 2

Upvotes: 0

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