grep using output from another command

Question

Say I have command1 which outputs this:

b05808aa-c6ad-4d30-a334-198ff5726f7c
59996d37-9008-4b3b-ab22-340955cb6019
2b41f358-ff6d-418c-a0d3-ac7151c03b78
7ac4995c-ff2c-4717-a2ac-e6870a5670f0

I also have command2 which outputs this:

b05808aa-c6ad-4d30-a334-198ff5726f7c
59996d37-9008-4b3b-ab22-340955cb6019

Is there a way to grep the output from command1 to not include any lines matched from command2, so that the final output would look like this?

2b41f358-ff6d-418c-a0d3-ac7151c03b78
7ac4995c-ff2c-4717-a2ac-e6870a5670f0

Probably doable with sort and awk

Basile Starynkevitch
– Basile Starynkevitch

2014-05-07 04:49:33 +00:00
Commented May 7, 2014 at 4:49 — Basile Starynkevitch
– Basile Starynkevitch, Commented May 7, 2014 at 4:49
Are those lines? If so, yes.

Jiminion
– Jiminion

2014-05-07 04:50:23 +00:00
Commented May 7, 2014 at 4:50 — Jiminion
– Jiminion, Commented May 7, 2014 at 4:50

Shiplu Mokaddim · Accepted Answer · 2014-05-07 05:18:13Z

29

Issue this grep

command1 | grep -vF -f <(command2)

Here,

-F means Fixed string match*

-v means invert match

-f means the file with patterns

<(command) actually creates a FIFO with that command and use it on redirection.

edited May 7, 2014 at 5:18

answered May 7, 2014 at 4:53

Shiplu Mokaddim

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1 Comment

bruchowski Over a year ago

Perfect thanks, I was missing the <() part, didn't know you could do that

John1024 · Accepted Answer · 2014-05-07 04:53:38Z

6

To get all the lines from the output of command1 that do not appear in the output of command2:

grep -vFf <(command2) <(command1)

-f tells grep to use patterns that come from a file. In this case, that file is the output of command2. -F tells grep that those patterns are to be treated as fixed strings, not regex. -v tells grep to invert its normal behavior and just show lines the lines that do not match.

answered May 7, 2014 at 4:53

John1024

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1 Comment

bruchowski Over a year ago

Thanks John, I upvoted you, but I marked the other answer just because I like the syntax better

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