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I have been trying to write a script that will checks if the specific content is not found in specific files/folders then it should print "failed". else it should print "success". However, the following script causing multiple errors.

if [[ ( ! grep '/example.com' /opt/nfs &>/dev/null ) || ( ! grep -R '/example.com' /data &>/dev/null) ]]
then
echo "Failed"
else
echo "Passed"
fi

Can anyone tell me why it's causing errors and is there anyway to eliminate the errors and get the expected output?

UPDATE: I'm getting following errors:

s.sh: line 1: conditional binary operator expected
s.sh: line 1: expected `)'
s.sh: line 1: syntax error near `'/example.com''
s.sh: line 1: `if [[ ( ! grep '/example.com' /opt/nfs &>/dev/null ) || ( ! grep -R '/example.com' /data &>/dev/null) ]]'
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4
  • what errors? ... Commented Oct 10, 2017 at 10:50
  • Hu @RomanPerekhrest, I have updated my question with errors. Thanks. Commented Oct 10, 2017 at 10:53
  • Most probably the use of & in the if statement. Also there is no need to redirect to /dev/null as you can use grep -q (quiet) instead Commented Oct 10, 2017 at 11:11
  • Read Simple logical operators in Bash Commented Oct 10, 2017 at 18:55

4 Answers 4

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[[...]] is a construct used to perform comparisons and other sorts of tests. It's a ksh command whose parsing follows special syntax rules and replaces the [ standard command (with normal simple command parsing).

Here, it's of no use. It's whether grep the grep command succeeds that you want to test (not a [[...]] or [ command), so it's just:

if grep -qF /example.com /opt/nfs || grep -RqF /example.com /data
then echo passed
else echo failed
fi

-q suppresses the output and also optimises by exiting as soon as one match is found instead of trying to find all matches.

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  • Hi @StéphaneChazelas I would like to try this in a reverse way as follows " if ! grep -q /example.com /opt/nfs || ! grep -Rq /example.com /data then echo failed else echo passed fi" But I didn't get expected output. Is there any wrong with above reverse script? Commented Oct 10, 2017 at 14:22
  • @BuvaneshKumar, are you sure it's a || and not a && that you meant? Do you want /example.com to be found in neither /opt/nfs nor /data (&&) or either not found in /opt/nfs or not found in data (||)? ! { A || B; } is ! A && ! B Commented Oct 10, 2017 at 14:38
  • I am sure, it's a | | and not a &&. Commented Oct 10, 2017 at 15:28
3

Straight-forward way:

grep -q '/example.com' /opt/nfs || grep -Rq '/example.com' /data
if [ $? -eq 0 ]; then   # check exit status
    echo "Passed"
else 
    echo "Failed"
fi

  • grep's -q option tells do not write anything to standard output. Exit immediately with zero 0 status if any match is found, even if an error was detected.

  • $? - contains exit status code of the last command run

The above could be also simplified to:

if grep -q '/example.com' /opt/nfs || grep -Rq '/example.com' /data; then
    echo "Passed"
else 
    echo "Failed"
fi
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  • Working great. thank you so much for the explanation. Commented Oct 10, 2017 at 11:52
  • @BuvaneshKumar, you're welcome Commented Oct 10, 2017 at 11:54
  • 3
    [ $? -eq 0 ] is a bit pointless as a command. That's a command that returns a 0 exit status if the previous exit status was 0. Doing if grep.... directly would make more sense. Commented Oct 10, 2017 at 12:34
  • @StéphaneChazelas, you have my note Commented Oct 10, 2017 at 13:45
3

Here is a possible simplification of your solution:

  • First of all, if you are using GNU grep, it can search in multiple file|folders provided in argument line. So basically no need to launch two grep command for looking to the same pattern in two different folders : grep '/example.com' /opt/nfs /data does the job for searching occurence of /example.com in those two folders.
  • Second two negations equal a positive. So why not simply use this code : if grep -rq "/example.com" /opt/nfs /data ; then echo "success" ; else echo "failed" ; fi grep will be successfull if it finds occurence of "/example.com" either in /opt/nfs or in /data

It will be faster, and more efficient, only one grep spawned from the shell.

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  • Good point. (note that all greps can search in multiple files, it's not just GNU grep; however -r/-R was initially a GNU grep feature and depending on the version both are not necessarily the same). Commented Oct 10, 2017 at 19:23
  • I was not sure about others grep i only have Gnu version at hand. Commented Oct 10, 2017 at 20:55
  • After looking again at the OP and my solution, i conclude my solution is not valid. The OP only succeed if /example.com is present in both folder /opt/nfs and /data, it fails in all other situation. grep is unable to handle that in one invocation. Commented Oct 10, 2017 at 21:53
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Try like this:

if [[ ! $(grep '/example.com' /opt/nfs &>/dev/null) || ! $(grep -R '/example.com' /data &>/dev/null) ]]
then
echo "Failed"
else
echo "Passed"
fi

But i think your script does not make sense because you suppress stdout and stderr with &>/dev/null. The output of your grep command always will be empty. Replace & to 2 to suppress stderr only.

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