grep to find word in files


$ man grep

-r search recursively if the given path is a directory
-i case-insensitive search
-n print the line number

-H print the filename [implied when multiple files are searched, i.e. no need to add -H
when the given path stands for mutliple files]

-I ignore binary files (complement: -a treat all files as text)
-F treat search term as a literal, not a regular expression


--exclude=GLOB
Skip files whose base name matches GLOB (using wildcard
matching). A file-name glob can use *, ?, and [...] as
wildcards, and \ to quote a wildcard or backslash character
literally.

--exclude-from=FILE
Skip files whose base name matches any of the file-name globs
read from FILE (using wildcard matching as described under
--exclude).

--exclude-dir=DIR
Exclude directories matching the pattern DIR from recursive searches.
[ e.g, to exlcude .svn and .git
xxx $ grep -r "non-sense" --exclude-dir='\.svn|\.git' (regex not supported for --exclude-dir ??)
--> $ grep -r "non-sense" --exclude-dir=.svn --exclude-dir=.git

http://superuser.com/questions/66715/recursive-grep-exclude-specific-directories

http://stackoverflow.com/questions/19962645/bash-function-grep-exclude-dir-not-working
the version of grep may not be able to use --exclude-dirs.

]


-E, --extended-regexp
-e PATTERN, --regexp=PATTERN
Use PATTERN as the pattern. This can be used to specify
multiple search patterns, or to protect a pattern beginning with
a hyphen (-). (-e is specified by POSIX.)



-R, --dereference-recursive
Read all files under each directory, recursively. Follow all
symbolic links, unlike -r.




-w, --word-regexp [to find a string that is a separate word (enclosed by spaces)]
Select only those lines containing matches that form whole
words. The test is that the matching substring must either be
at the beginning of the line, or preceded by a non-word
constituent character. Similarly, it must be either at the end
of the line or followed by a non-word constituent character.
Word-constituent characters are letters, digits, and the
underscore.


-L, --files-without-match [only print filenames that are not matched]
Suppress normal output; instead print the name of each input
file from which no output would normally have been printed. The
scanning will stop on the first match.

-l, --files-with-matches [only print the matching filenames]
Suppress normal output; instead print the name of each input
file from which output would normally have been printed. The
scanning will stop on the first match. (-l is specified by
POSIX.)


[examples]
$ grep -r word_to_find .
[to search "word_to_find" recursively under the current directory ]


$ grep -n "> tmp1.txt" *.sh
[to find string "> tmp1.txt" in all files with extension name ".sh" in the current folder, not recursively]

xxx often mistake
$ grep myutil.js .
grep: .: Is a directory
xxx

-->
$ grep -r myutil.js .
$ grep myutil.js *.js
$ grep "myutil.js" *.js

$ grep *.js *.js
$ grep ".*js" *.js
[here, ".*js" stands for a regex in bash]

$ grep -l "> tmp1.txt" *.sh
[list all the names of files which contain "> tmp1.txt" ]

$ grep -r "myutil.js" . --exclude-dir=.git
$ grep -r "myutil.js" . --exclude-dir=?git
[though works as well, it means to exclude all subfolders whose name is even like agit, bgit, mgit, .git, etc. ]



[ref]
http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_04_02.html

bash regex
http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_04_01.html
http://tldp.org/LDP/abs/html/x17129.html

http://ubuntu.elfscript.com/2013/09/ubuntu.html