Rhel 7 Grep Command

GREP Command in Unix and Linux Examples

                          

About Grep :

grep is a command-line utility for searching plain-text data sets for lines that match a regular expression

 

Grep Linux Command	Grep Linux Command Description
grep book /etc/passwd	command to search book in a file
grep -i "book" /etc/passwd	To ignore word case i.e match book, Book, BOOK and all other combination with the -i option:
grep -R "192.168.1.5" /etc/	You can search recursively i.e. read all files under each directory for a string “192.168.1.5”
grep -w "book" file	The grep command to select only those lines containing matches that form whole words i.e. match only book word:
egrep -w 'word1|word2' /path/to/file	Use grep to search 2 different words
grep -c 'word' /path/to/file	The grep can report the number of times that the pattern has been matched for each file using -c (count) option
grep -n 'root' /etc/passwd	Pass the -n option to precede each line of output with the number of the line in the text file from which it was obtained
grep -v mars /path/to/file	You can use -v option to print inverts the match; To print all line that do not contain the word mars:
dmesg | egrep '(s|h)d[a-z]'	show the name of the hard disk devices:
grep -i 'Model' /proc/cpuinfo         or	Display cpu model name:
$ grep --color vivek /etc/passwd	force grep to display output in colors, enter:
$ grep -v -c this demo_file	how many lines that does not match the pattern

Grep Command	Grep command Description
grep -o -b "string" file.txt	Displaying the position of the matched string in the line The -b option allows the grep command to display the character position of the matched string in a file.
grep -B 2 "Error" file.txt	Displaying the lines before the match. In log file it will tell lines around the error lines to know the cause of the error. This will prints the matched lines along with the two lines before the matched lines.
grep -A 3 "Error" file.txt	Displaying the lines after the match. This will display the matched lines along with the three lines after the matched lines.
grep -C 5 "Error" file.txt	Displaying the lines around the match This will display the matched lines and also five lines before and after the matched lines
$ export GREP_OPTIONS='--color=auto' GREP_COLOR='100;8	It will set the color for Matched Line and pattern found will be color