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jwilk · 2018-01-06 19:44:05+00:00

    $ grep somestring file1 > /tmp/a
    $ grep somestring file2 > /tmp/b
    $ diff /tmp/a /tmp/b

You shouldn't do that, but not because it's not neat enough. /tmp is world-writable, so you might be writing to somebody else's file, or over a symlink that was set up by someone else. Use mktemp¹ for creating temporary files.

¹ http://man7.org/linux/man-pages/man1/mktemp.1.html

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erk__ | karma 2323 | avg karma 3.24 · | 2018-01-06 20:00:21

Could you not do that with pipes instead, something like:

    $ diff <(grep somestring file1) <(grep somestring file2)

pixelbeat | karma 1110 | avg karma 9.02 · | 2016-09-23 15:13:33+00:00

Thanks for the detailed comparisons and writeup.

I find this simple wrapper around grep(1) very fast and useful:

http://www.pixelbeat.org/scripts/findrepo

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pmlnr | karma 11277 | avg karma 4.01 · | 2017-06-14 11:14:28+00:00

text files + syncthing + grep

https://syncthing.net/

https://stackoverflow.com/questions/87350/what-are-good-grep...

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monocasa | karma 27236 | avg karma 2.94 · | 2022-05-11 09:58:04

    $ file /sbin/* | grep "dynamically linked" | wc -l
    325

    $ file /sbin/* | grep -i "static" | wc -l
    0

On Ubuntu focal, but Red Hat is similar.

JdeBP | karma 6361 | avg karma 1.77 · | 2016-04-25 11:45:56

... although that is a canonical Useless Use of grep. (-:

* http://porkmail.org/era/unix/award.html#grep

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jonjacky | karma 801 | avg karma 1.43 · | 2019-11-11 11:04:17

http://www.redballoon.net/humor/unix1.txt

A is for Awk, which runs like a snail, and B is for Biff, which reads all your mail. ...

but the grep entry here is different from what you remember.

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hrwl | karma 12 | avg karma 1.33 · | 2013-09-11 10:39:48

   <file grep xyz

works in bash for one.

uselessuseof | karma 1 | avg karma 0.09 · | 2012-06-07 14:16:13

does your grep have an -f option?

   printf linkedintrouble |sha1sum |sed 's/ .*//' |grep -f - combo_not.txt

ribasushi | karma 348 | avg karma 3.48 · | 2022-05-23 01:58:09

FWIW redirection is not positional:

    ~$ <frongle.txt grep fringle >frungle.txt

xyzwave | karma 408 | avg karma 4.34 · | 2022-02-19 10:29:37

Somewhat tangential, but the author calls out using `grep` in conjunction with `awk`. Anytime I find myself doing this, it usually turns out that I can just throw the pattern into AWK itself.

    grep 'foo' file.txt | awk '{ print $1 }'

Becomes:

    awk '/foo/ { print $1 }' file.txt

There may be times when `grep` is preferable, but this is ubiquitous enough that it's mentioned in the "Useless Use of Cat" [1] awards.

[1] https://porkmail.org/era/unix/award

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mdekkers | karma 1684 | avg karma 1.32 · | 2024-02-22 06:48:42

> grep filename.txt “thing I want”

> grep “thing I want” filename.txt.

…every time

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asdff | karma 12593 | avg karma 1.54 · | 2020-12-04 07:49:52+00:00

I prefer keeping it all in one file, less messy since you are using grep anyway:

alias note='(date; cat; echo) >> ~/notes.txt'

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justin_oaks | karma 3123 | avg karma 3.98 · | 2021-05-03 13:53:05

I think

    grep ^ *

would fix that and is just as short.

forgotpwd16 | karma 2758 | avg karma 1.8 · | 2022-10-13 07:15:38

That's what GNU grep recommends: https://www.gnu.org/software/grep/manual/html_node/Usage.htm...

discreditable | karma 4405 | avg karma 5.55 · | 2017-05-22 12:32:27

One of my favorite moreutils tools is combine[1]. It allows you to compare the contents of text files with boolean operations. For example, want to know what lines are in file1 but not file2? Use:

    combine file1 not file2

1. http://manpages.ubuntu.com/manpages/zesty/en/man1/combine.1....

philsnow | karma 4551 | avg karma 2.16 · | 2015-01-18 21:49:07

fwiw

    $ <filename grep <pattern>

no shell I'm aware of restricts you to placing redirections at the end, you can throw them on the beginning no problem.

dossy | karma 197 | avg karma 1.3 · | 2022-04-13 08:19:17

uh...

$ grep remote files/* | grep "machine learning"

you're welcome?

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Animats | karma 143047 | avg karma 6.11 · | 2017-04-17 18:44:46+00:00

I use

   ***TEMP***, 
   ***NEEDS WORK***, etc.

Those you can find with grep.

(HN needs less broken Markdown.)

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koprulusector | karma 436 | avg karma 3.43 · | 2022-10-13 09:50:01

Thanks for sharing. I feel less silly for suggesting this now (as root):

    unalias grep && unalias egrep && cp "$(command -v grep)" "$(dirname "$(command -v grep)")/egrep