小屋 : some tips for grep

Some tips for grep

  Global-Regular-Expression-Print(GREP) is a command line text search utility used in Unix & Unix-like system.

  The “grep” command searches files or standard input for lines that match a given regular expression. It then prints the matching lines to the program’s standard output.

The basic options

• “-i” Ignore case sensitivity.

• “-b” Display block numbers at the begining of every line.

• “-n” Display matches lines and line numbers.

• “-v” Display lines that do not match.
• “-o” Show only the matched string.
• “-l” Display only the file names which matches the given pattern.
• “-r” Search a string recursively in all Directories.

####1, Grep for a string, but show the preceding 5 lines and following 5 lines as well as the matched the line.

-B number to set how many lines before the match and -A number for the number of lines after the match.

grep -B number -C number searchstring file

-C number to get the same amount of lines before and after the match.

grep -C number searchstring file

####2, Checking for full words, not for sub-strings using -w.

grep -iw "string" file

####3, Counting the number of matches.

grep -c "pattern" file

####4, Search a string in Gzipped files.

grep -i searchstring file

####5, Match regular expression in files.(egrep)

grep -E

####6, Search a Fixed Pattern String.(fgrep)

grep -F