grep common usage

About grep

As described in the man file for Linux:

   grep  searches  the  named  input  FILEs (or standard input if no files are named, or if a single hyphen-minus (-) is given as file name) for lines containing a match to the given PATTERN.  By default, grep prints the matching lines.   In addition, two variant programs egrep and fgrep are available.  egrep is the same as grep -E.   fgrep  is  the  same  as  grep -F.   Direct invocation as either egrep or fgrep is deprecated, but is provided to allow historical applications that rely on them to run unmodified.

grep is a command used to find rows in a file that matches a given pattern, while both Egrep and fgrep have been deprecated and replaced by GREP-E and Grep-f.

Using methods to search a single file for rows that contain strings

Grammar:
grep "literal_string" filename

Searching for rows containing strings in multiple files

Grammar:
grep "This" demo_*
Note: This search domain is a file prefixed with Demo_

Use the-I parameter to enable case-insensitive use of regular expressions to filter

Grammar:
grep "REGEX" filename

Specific use of the method can be consulted: http://www.cnblogs.com/kuyuecs/archive/2012/07/13/2589988.html
Well-written blog.

grep common usage