grep Command
[ Examples ]
“Grep” command is use to search for a given file for line
containing some word, string.
By default grep display the matching lines. Use grep to
search for lines of text that match one or many regular expressions, and
outputs only the matching lines
grep command can run in both linux and unix in their
command editors.
Grep
command syntax
grep 'word'
filename
grep 'string1
string2' filename
cat otherfile | grep 'something'
command | grep 'something'
command option1 | grep 'data'
grep --color 'data'
filename
how
to use gre to seach a file?
Search /etc/passwd for vicky user:
$ grep vicky /etc/passwd
$ grep vicky /etc/passwd
You can force grep to ignore word
case i.e match Vicky, Vicky, VICKY and all other combination with -i option:
$ grep -i "vicky" /etc/passwd
$ grep -i "vicky" /etc/passwd
Use
grep recursively
You can search recursively i.e. read
all files under each directory for a string "192.168.1.5"
$ grep -r "192.168.1.5" /etc/
$ grep -r "192.168.1.5" /etc/
Use
grep to search words only
When you search for vicky, grep will
match yovicky, vicky123, etc. You can force grep to select only those lines
containing matches that form whole words i.e. match only vicky word:
$ grep -w "boo" /path/to/file
$ grep -w "boo" /path/to/file
Use
grep to search 2 different words
use egrep as follows:
$ egrep -w 'word1|word2' /path/to/file
$ egrep -w 'word1|word2' /path/to/file
Count
line when words has been matched
grep can report the number of times
that the pattern has been matched for each file using -c (count) option:
$ grep -c 'word' /path/to/file
Also note that you can use -n option, which causes grep to precede each line of output with the number of the line in the text file from which it was obtained:
$ grep -n 'word' /path/to/file
$ grep -c 'word' /path/to/file
Also note that you can use -n option, which causes grep to precede each line of output with the number of the line in the text file from which it was obtained:
$ grep -n 'word' /path/to/file
UNIX
/ Linux pipes and grep command
Display cpu model name:
# cat /proc/cpuinfo | grep -i 'Model'
However, above command can be also used as follows without shell pipe:
# grep -i 'Model' /proc/cpuinfo
# cat /proc/cpuinfo | grep -i 'Model'
However, above command can be also used as follows without shell pipe:
# grep -i 'Model' /proc/cpuinfo
How
do I list just the names of matching files?
Use the -l option to list file name
whose contents mention main:
$ grep -l 'main' *.c
Finally, you can force grep to display output in colors:
$ grep --color vivek /etc/passwd
Sample outputs:
$ grep -l 'main' *.c
Finally, you can force grep to display output in colors:
$ grep --color vivek /etc/passwd
Sample outputs:
Grep command in action
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