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Grep flags – the good stuff

zwischenzugs.com

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Re: Grep flags – the good stuff

#22

Post by addingnumbers »

mmh0000 wrote: post #4

An amazing grep trick that I use all the time: The -e flag can be used to search for multiple terms. A blank -e will search for null. Thus: Lets assume we have a log file with a bunch of relevant stuff, I want to highlight my search term, BUT I also want to keep all the other lines around for context: $ dmesg ...SNIP... [2334597.539661] sd 1:0:0:0: [sdb] Attached SCSI removable disk [2334597.548919] sd 1:0:0:0: [sdb]…

I always used "-e ^" the same way you're using a null string, to show all lines of the files, each prefixed with the path and filename. Are they equivalent or is there a caveat I should watch out for?

Re: Grep flags – the good stuff

#23

Post by rustyminnow »

zwieback wrote: post #3

Ah, learned the difference between -i and -I. I also like --include and --exclude, especially since it allows regex for which files to look at

If you need to include/exclude multiple things, you can go `grep pat --exclude={foo,bar,baz}` which expands to: `grep pat --exclude=foo --exclude=bar --exclude=baz`. Much easier than typing out the flag multiple times

Re: Grep flags – the good stuff

#24

Post by likpok »

addingnumbers wrote: post #22
mmh0000 wrote: post #4

An amazing grep trick that I use all the time: The -e flag can be used to search for multiple terms. A blank -e will search for null. Thus: Lets assume we have a log file with a bunch of relevant stuff, I want to highlight my search term, BUT I also want to keep all the other lines around for context: $ dmesg ...SNIP... [2334597.539661] sd 1:0:0:0: [sdb] Attached SCSI removable disk [2334597.548919] sd 1:0:0:0: [sdb]…

I always used "-e ^" the same way you're using a null string, to show all lines of the files, each prefixed with the path and filename. Are they equivalent or is there a caveat I should watch out for?

Zsh (and possibly other shells?) will expand a raw ^ into filenames. '' is a little shorter than '^' if you have to quote it.

Re: Grep flags – the good stuff

#25

Post by CalChris »

I have a shell alias/function variations of which I've used for decades. This is the zsh version:

  function fvi { grep -rl $1 . | xargs nvim +/$1 }
It greps a directory recursively and opens files which have a pattern and puts the pattern in the search buffer.

Re: Grep flags – the good stuff

#27

Post by js2 »

In my PATH I have this script as git-gsr, which I can call as "git gsr".

    #!/bin/sh
    
    usage () {
        cat >&2   [paths...]
    
      replace all occurrances of  with  optionally limited to
       (as interpreted by git grep)
    
      -P, --perl-regexp     interpret  as perl regular expression;
                            default is to treat it as a fixed string.
    
    __USAGE__
        exit 1
    }
    
    pattern='-F'
    perl='BEGIN {($old, $new) = (shift, shift)} s/\Q$old\E/$new/g'
    
    case "$1" in
        -P|--perl-regexp)
            shift
            pattern='-P'
            perl='BEGIN {($old, $new) = (shift, shift)} s/$old/$new/g'
            ;;
        -*) usage
            ;;
    esac
    test $# -lt 2 && usage
    old=$1; new=$2; shift; shift
    git grep -l -z $pattern "$old" -- "$@" |
    xargs -0 perl -pi -e "$perl" "$old" "$new"

Re: Grep flags – the good stuff

#28

Post by aidenn0 »

bloopernova wrote: post #16
aidenn0 wrote: post #11

I think I have never used grep -r. I'm sure gnu grep has some way to specify which files to search, but why would I learn that syntax as well when I already know find, and exec works (exec + is much faster, but exec ; gets you the results too if your find lacks exec +).

Check out ripgrep

I'm aware of rg, ag, &c. these tools. I even wrote a clone of ag in shell using find/grep/xargs (the last one being needed to get parallelism to match ag's speed).

Re: Grep flags – the good stuff

#29

Post by cjcampbell »

simon04 wrote: post #12

https://explainshell.com/explain?cmd=grep+-rilIv

And explainshell might be my favorite discovery of the day. I hadn't stumbled on it before now. I think it'll be helpful for folks I mentor/train. I do push everyone toward using the man pages directly, but I can see how this would be less intimidating for a beginner.
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