Can I grep for multiple patterns but have some be inverse?

Question

I know that I can search for multiple patterns like so

    grep -e 'pattern1|pattern2' file

and I can invert the grep search like so

    grep -v 'pattern' file

but is there a way I can grep for one pattern while simultaneously doing an inverse grep for another?

    grep -e 'pattern I want' -v 'pattern I do not want' file

With PCRE patterns, yes. That is, you need a GNU grep, or pcregrep. — Wiktor Stribiżew, Feb 18 '19 at 20:39
@WiktorStribiżew - what would that look like? I'm not doubting your words, just genuinely curious as I haven't seen such use with grep yet ... — tink, Feb 18 '19 at 21:16
The classic idiom is `grep a | grep -v b`, but we can do better than two procs, right? :) — Paul Hodges, Feb 18 '19 at 21:55

score 10 · Accepted Answer · answered Feb 18 '19 at 20:43

10

You may use awk as an alternative:

awk '/pattern I want/ && !/pattern I do not want/' file

answered Feb 18 '19 at 20:43

anubhava

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score 2 · Answer 2 · answered Feb 18 '19 at 21:47

Assuming suitably quoted patterns,

 sed -n "/$pat1/ { /$pat2/ d; p; }" file

-n tells sed not to print unless explicitly requested.
/$pat1/ { ... } says on lines matching $pat1, execute the commands in the braces.
/$pat2/ d; says on lines with $pat2, delete, which automatically cycles to the next line of input and ignores any more commands for this line, skipping the p. If it does not see $pat2, the d doesn't fire and proceeds to...
p means print the current line.

My example:

$: grep '#if ' dcos-deploy.sh
#if   (( ${isPreProd:-0} ))
#if [[ "$target_mesosphere_cluster" != CDP ]]

$: pat1="^#if "
$: pat2="\\[\\["

$: sed -En "/$pat1/ { /$pat2/ d; p; }" dcos-deploy.sh
#if   (( ${isPreProd:-0} ))

Can I grep for multiple patterns but have some be inverse?

2 Answers2