CODEWITHSUNDEEP
shellunixgrep
tba
tba

Reputation: 6571

Grep behavior on OS X with --only-matching

When I run the following:

printf "1234\n1234" | grep -o '^.'

I get the following output on OSX 10.10 with zsh 5.0.5:

1
2
3
4
1
2
3
4

Why? I'd expect this output instead:

1
1

Can anyone reproduce this issue? I get the expected output on Ubuntu 14.04.

Upvotes: 3

Views: 2163

Answers (2)

kojiro
kojiro

Reputation: 77137

The problem seems to be that Apple has elected to have a more-than-a-decade-old version of grep on its latest operating system. It has bugs including the one you point out. The only thing I can seriously suggest is that you use a package manager like homebrew to upgrade the grep you use for day-to-day work.

$ grep --version
grep (BSD grep) 2.5.1-FreeBSD
$ grep --color=never -o ^. <<< ab
a
b
$ brew install grep
==> Installing grep from homebrew/homebrew-dupes
<SNIP>
$ ggrep --version
ggrep (GNU grep) 2.21
$ ggrep --color=never -o ^. <<< ab
a

Upvotes: 7

Jotne
Jotne

Reputation: 41456

I can not tell you what is wrong, but try a workaround:

printf "1234\n1234" | awk -vFS= '{print $1}'
1
1

By setting FS to nothing, every characters become separate fields, then print first field $1

If -FS= does not work try -vFS=""

Upvotes: 0

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