Difference between revisions of "grep"
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| + | <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
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