Bash conditional statement zero/nonzero unexpected results

Asked Jan 15 '20 at 21:05

Active Jan 15 '20 at 21:08

Viewed 23 times

In file.txt, I've got the following lines:

word1 blahbla
word2 blahbla
..........

Grep works as expected.

grep "word1.*word2" file.txt

gives me output, which I expect, because word1 occurs before word2.

grep "word2.*word1" file.txt

gives no output, which I expect, because word 2 occurs after word1 and not before it.

The conditional statement does not work as expected.

[ -n '$(grep "word1.*word2" file.txt' ] && echo "output" || echo "no output"

gives me expected result, echoing "output", but ...

[ -n '$(grep "word2.*word1" file.txt' ] && echo "output" || echo "no output"

gives me UNEXPECTED result, echoing "output" when I'm expecting "no output".

What's wrong?

edited Jan 15 '20 at 21:08

Barmar

asked Jan 15 '20 at 21:05

oksage

Command substitution doesn't happen inside single quotes. – Barmar Jan 15 '20 at 21:09
You're just testing the literal strings, not executing `grep`. – Barmar Jan 15 '20 at 21:10
1

You're also missing `)`. – Barmar Jan 15 '20 at 21:10
Also, the default behavior of grep is to not match strings spanning multiple lines, so I wouldn't expect `grep "word1.*word2"` to match – HardcoreHenry Jan 15 '20 at 21:16

0 Answers0