I've recently started learning sed. I did
$seq 10 | sed '/[^049]/d'
I was expecting
4
9
10
as output. But I got
4
9
Where am I making mistake in understanding this regex?
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2 Answers
The 1 in the number 10 matches [^049] so it's deleted.
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Whoops. That was foolish of me to ask here. :( Thanks by the way.Dharmit– Dharmit2011-04-27 02:09:31 +00:00Commented Apr 27, 2011 at 2:09
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1Minor tip: Bracketing your regex with
^and$is useful to ensure that you're always looking at the whole string.l0b0– l0b02011-04-27 09:48:39 +00:00Commented Apr 27, 2011 at 9:48
If you really want to show lines containing '0', '4', or '9', here's how:
seq 10 | sed -n '/[049]/p'
The -n instructs sed to not print any lines. The p command instructs sed to print lines matching the /regex/
Alternatively, you can always use grep :-)
seq 10 | grep -E "[049]"
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This is valid, but the exact approach the OP was looking for was probably:
seq 10 | sed '/[049]/!d'This deletes any lines that do not match[049]rather than deleting any lines which match "not 049", aka[^049].Wildcard– Wildcard2015-11-19 00:20:07 +00:00Commented Nov 19, 2015 at 0:20