grep command options
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The grep is the Unix utility that filter searches a file for a particular pattern of characters and displays all lines that contain that pattern.
Grep stands for globally search for regular expression and prints out
Syntax:
Options
Command-line options switches of grep:
- -e pattern expression with this option
- -i: Ignore uppercase vs. lowercase, can say the case for matching
- -v: Invert match means prints out all the lines that do not match the pattern
- -c: Prints output count of matching lines only.
- -l: Output matching files (list of filenames) only.
- -n: Prints matching line with a line number.
- -b: A historical curiosity: Prints each matching line with a block number.
- -h: Output matching lines without showing them by file names.
- -s: Output status only.
- -f file: Take regexes from a file.
- -w: Match whole word
- -o: To display only the matched pattern
Command-line options switches of GNU grep :
- –help
- -V, –version
- –regexp=pattern, in addition to -e pattern
- –invert-match, in addition to -v
- –word-regexp, in addition to -w
- –line-regexp, in addition to -x
- -A num, –after-context=num
- -B num, –before-context=num
- -C num, -num, –context=num
Syntax :
grep [options] pattern [files]
Sample Commands
$ ls
Site.sh cron.txt openssl-1.0 xyz abc unix.txt
$ ls |grep cron
cron.txt
On the contrary, if you want to filter a list unless some entries, put it in the parameter -v:
$ ls | grep -v
Site.sh
cron.txt
openssl-1.0
xyz
abc
unix.txt
Consider the below :
$cat > unix.txt
unix is opensource. unix is great os. unix is great os.
unix is a multiuser os.
Unix linux which one you choose. learn operating system. uNix is easy to learn. Learn unix .unix is a powerful.
Option : -i (Ignore uppercase vs. lowercase, can say the case for matching)
$grep -i "UNix" unix.txt
Output:
unix is opensource. unix is great os. unix is great os.
unix is a multiuser os.
Unix linux which one you choose. learn operating system. uNix is easy to learn. Learn unix .unix is a powerful.
Option: -c (Prints output count of matching lines only)
$grep -c "unix" unix.txt
Output:
3
Option: -l (Output matching files (list of filenames) only.
grep -l "unix" *
Output :
unix.txt
Option : -w (Match whole word)
grep -w "unix" unix.txt
Output :
unix is opensource. unix is great os. unix is great os.
unix is a multiuser os.
Unix linux which one you choose. learn operating system. uNix is easy to learn. Learn unix .unix is a powerful.
Option : -o (To display only the matched pattern)
grep -o "unix" unix.txt
Output :
unix
unix
unix
unix
unix
unix
Option : -n (Prints matching line with a line number)
grep -o "unix" unix.txt
Output :
1:unix is opensource. unix is great os. unix is great os.
2:unix is a multiuser os.
3:Unix linux which one you choose. learn operating system. uNix is easy to learn. Learn unix .unix is a powerful.
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