4 ms·

"One thing" has never been very well defined - basically every common Linux shell tool could be said to do more than one thing. GNU `grep` supports four differe

by l0b0 8y ago

"One thing" has never been very well defined - basically every common Linux shell tool could be said to do more than one thing. GNU `grep` supports four different pattern styles (fixed strings, basic regex, extended regex and Perl regex), has lots of options for output formatting (counting, line numbers, whether to display file names, etc.) and has a bunch of rarely-used (but useful!) options for various corner cases, such as line buffering. Even GNU `cat`, the canonical "do one thing" tool, has several formatting options. If `grep` returned match objects rather than a semantically void binary stream it would be really easy to hand over formatting to another tool, but that just isn't how *nix tools work yet.

bradknowles 8y ago
The thing I would like to see with grep is to have it optionally give me a 0 return code if it doesn't find anything. I know why the authors chose to use a non-zero return code as the default, but when I'm using grep deep in a pipeline and doing my own checking of the results to see if nothing was found, I don't need grep bombing out the whole pipeline with a non-zero return code. The alternative of being forced to use "(grep pattern||true)" instead of a plain "grep -q" is kinda painful.
- vitorbaptistaa 8y ago
  I'm not in my computer now, but doesn't "grep -v" solves your issue? If I remember correctly, it inverts the query, so it would return 0 if there wasn't a match.
  - Sean1708 8y ago
    No, -v will return 0 unless every line matches: $ cat > foo here's some random text $ grep -v some foo; echo $? here's random text 0 $ grep -v bar foo; echo $? here's some random text 0 $ grep -vE "(here's|some|random|text)" foo; echo $? 1
- mangamadaiyan 8y ago
  Would grep -c work for your use-case?
- Pete_D 8y ago
  How about "awk /pattern/"?
Sean1708 8y ago
> Even GNU `cat`, the canonical "do one thing" tool, has several formatting options. Huh, TIL. It's just never occurred to me to even bother checking the help for cat. $ cat --help Usage: cat [OPTION]... [FILE]... Concatenate FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines, overrides -n -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit Examples: cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/cat> or available locally via: info '(coreutils) cat invocation'

by l0b0 8y ago

bradknowles 8y ago

The thing I would like to see with grep is to have it optionally give me a 0 return code if it doesn't find anything. I know why the authors chose to use a non-zero return code as the default, but when I'm using grep deep in a pipeline and doing my own checking of the results to see if nothing was found, I don't need grep bombing out the whole pipeline with a non-zero return code. The alternative of being forced to use "(grep pattern||true)" instead of a plain "grep -q" is kinda painful.

vitorbaptistaa 8y ago
I'm not in my computer now, but doesn't "grep -v" solves your issue? If I remember correctly, it inverts the query, so it would return 0 if there wasn't a match.
- Sean1708 8y ago
  No, -v will return 0 unless every line matches: $ cat > foo here's some random text $ grep -v some foo; echo $? here's random text 0 $ grep -v bar foo; echo $? here's some random text 0 $ grep -vE "(here's|some|random|text)" foo; echo $? 1
mangamadaiyan 8y ago
Would grep -c work for your use-case?
Pete_D 8y ago
How about "awk /pattern/"?

Sean1708 8y ago

> Even GNU `cat`, the canonical "do one thing" tool, has several formatting options. Huh, TIL. It's just never occurred to me to even bother checking the help for cat. $ cat --help Usage: cat [OPTION]... [FILE]... Concatenate FILE(s) to standard output. With no FILE, or when FILE is -, read standard input. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines, overrides -n -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit Examples: cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Full documentation at: <http://www.gnu.org/software/coreutils/cat> or available locally via: info '(coreutils) cat invocation'