Check for substring using unix make

Question

Coding in UNIX make, I have written:

cat $ sString | grep sSubstring > sResult

So I want to check if sString contains sSubString and, if it does, put the result in sResult.

Background: I have put the contents of a file in sString - if sSubString is present in the file, then sResult contains each line of the file containing sSubString.

This works fine when sSubString is in sString. When it is not, I get Error Code 1.

How can I handle this correctly? The complete code is:

cat $ sString | grep sSubstring > sResult
if [ -s sResult -gt 0 ];then \
(echo "substring present" ) \
else (echo "substring not present" ) ;fi

(With the error code, I never get to the else .)

FWIW, I've tried other other string contains solutions here, but those solutions do not work on this make file. — Reinstate Monica - Goodbye SE
– Reinstate Monica - Goodbye SE, Commented Oct 23, 2012 at 15:23

darkgrin · Accepted Answer · 2012-10-23 15:36:27Z

2

To check if a specific substring is present in a string, you can use the 'findstring' function. More info here: http://www.gnu.org/software/make/manual/html_node/Text-Functions.html.

answered Oct 23, 2012 at 15:36

darkgrin

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Community · Accepted Answer · 2017-05-23 11:55:56Z

1

Sounds like you might need this

cat $ sString | { grep sSubstring || true; } > sResult

See this solution. The problem is that when grep doesn't find anything it returns a non-zero exit code. make will then think it is an error. So you just need to make sure that the command always returns a zero exit code by or-ing the exit code of grep with the exit code of true. The exit code of true is always 0.

edited May 23, 2017 at 11:55

CommunityBot

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answered Oct 23, 2012 at 15:30

cyon

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1 Comment

Reinstate Monica - Goodbye SE Over a year ago

Amazing! That was quick, and it works perfectly. Thanks so much!

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