grep: Difference between revisions
from HTYP, the free directory anyone can edit if they can prove to me that they're not a spambot
extracted manpage transcrip to a subpage; reference links |
more notes |
||
| Line 1: | Line 1: | ||
<hide> | |||
[[page type::manual]] | |||
[[thing type::command]] | |||
[[platform::Linux]] | |||
</hide> | |||
==Pages== | ==Pages== | ||
* {{l/manpage}} - the current [[manpage]] | * {{l/manpage}} - the current [[manpage]] | ||
* [[/manpage]] - a nicely-formatted but old version of the grep manpage | * [[/manpage]] - a nicely-formatted but old version of the grep manpage | ||
==Examples== | |||
; grep ''text_to_find'' *.log:find ''text_to_find'' by checking all the logfiles in the current folder | |||
; grep -r ''text_to_find'' *:find ''text_to_find'' by checking all files in the current folder or under it | |||
==Questions== | ==Questions== | ||
* So, how do you grep for a string which contains spaces and quote characters? This is probably some standard feature of Linux Shell syntax which everyone knows, but I don't, and that's why this page needs examples. | * So, how do you grep for a string which contains spaces and quote characters? This is probably some standard feature of Linux Shell syntax which everyone knows, but I don't, and that's why this page needs examples. | ||
*: '''A''': Tentatively, you can surround a string with double-quotes and escape any quotes in the search-string with the backslash character. (Single quotes do not seem to work.) | |||
* Likewise, how do you search a group of files? Using "*.*" for FILE doesn't seem to work, and leaving the FILE argument blank tells grep to expect input from STDIN. | * Likewise, how do you search a group of files? Using "*.*" for FILE doesn't seem to work, and leaving the FILE argument blank tells grep to expect input from STDIN. | ||
*: '''A:''' apparently "*" by itself; see examples | *: '''A:''' apparently "*" by itself; see examples above | ||
==Notes== | |||
If ''file'' is specified using wildcards (e.g. *.log or *), apparently the command-line parser expands this into a listing of all matching files before passing it to grep. This unfortunately can lead to the error "bash: /bin/grep: Argument list too long". Putting a backslash before the wildcard will prevent the parser from expanding it before passing to grep, but grep doesn't seem to have any wildcard-handling abilities. So as far as I can tell, there is no way to grep a really large directory (the one I'm looking at has 5014 files). | |||
The -r option doesn't seem to work if a file extension is specified (e.g. "*.log" in the example above), though it does work with "*". There may be some syntax which needs to surround "*.log* -- or maybe this simply is not doable using the inline-expansion method of handling wildcards? | |||
The backtick character ("`") seems to mean "insert the output of this command here" -- so if you're trying to search for a literal backtick, it needs to be escaped with "\" ("\`"). This comes up sometimes when searching for [[SQL]] phrases. | |||
==Links== | ==Links== | ||
* [http://www.gnu.org/software/grep/manual/ official documentation]: more current than the manpage | * [http://www.gnu.org/software/grep/manual/ official documentation]: more current than the manpage on this server | ||
* {{wikipedia}} | * {{wikipedia}} | ||
Revision as of 15:41, 8 April 2017
<hide> page type::manual thing type::command platform::Linux </hide>
Pages
Examples
- grep text_to_find *.log
- find text_to_find by checking all the logfiles in the current folder
- grep -r text_to_find *
- find text_to_find by checking all files in the current folder or under it
Questions
- So, how do you grep for a string which contains spaces and quote characters? This is probably some standard feature of Linux Shell syntax which everyone knows, but I don't, and that's why this page needs examples.
- A: Tentatively, you can surround a string with double-quotes and escape any quotes in the search-string with the backslash character. (Single quotes do not seem to work.)
- Likewise, how do you search a group of files? Using "*.*" for FILE doesn't seem to work, and leaving the FILE argument blank tells grep to expect input from STDIN.
- A: apparently "*" by itself; see examples above
Notes
If file is specified using wildcards (e.g. *.log or *), apparently the command-line parser expands this into a listing of all matching files before passing it to grep. This unfortunately can lead to the error "bash: /bin/grep: Argument list too long". Putting a backslash before the wildcard will prevent the parser from expanding it before passing to grep, but grep doesn't seem to have any wildcard-handling abilities. So as far as I can tell, there is no way to grep a really large directory (the one I'm looking at has 5014 files).
The -r option doesn't seem to work if a file extension is specified (e.g. "*.log" in the example above), though it does work with "*". There may be some syntax which needs to surround "*.log* -- or maybe this simply is not doable using the inline-expansion method of handling wildcards?
The backtick character ("`") seems to mean "insert the output of this command here" -- so if you're trying to search for a literal backtick, it needs to be escaped with "\" ("\`"). This comes up sometimes when searching for SQL phrases.
Links
- official documentation: more current than the manpage on this server
- Wikipedia
