GREP

• let's view the content of the file we are going to work with

[root@RHEL5-Serv01 work]# cat grepfile2
first line
second line
third line
fourth line
fifth line
seventh line
eighth line
nineth line
tenth line
ten lines in total contain the word line

• let's grep the word "ten"

[root@RHEL5-Serv01 work]# grep ten grepfile2
tenth line
ten lines in total containing the word line

• let's count the number of match

[root@RHEL5-Serv01 work]# grep -c ten grepfile2
2

•  ignoring case of the word

[root@RHEL5-Serv01 work]# grep TEN grepfile2
[root@RHEL5-Serv01 work]# 
※　NO MATCH BUT WHEN IGNORING CASE AS FOLLOWS
[root@RHEL5-Serv01 work]# grep -i TEN grepfile2

tenth line
ten lines in total containing the word line

• lets reduce the above result to an exact match

[root@RHEL5-Serv01 work]# grep -w ten grepfile2
ten lines in total containing the word line

• matching multiple words

[root@RHEL5-Serv01 work]# grep -e "first" -e "second" grepfile2
first line
second line
※ the following gives the same result as the command above
[root@RHEL5-Serv01 work]# grep -E 'first|second' grepfile2
first line
second line

• matching two lines after the matching word

[root@RHEL5-Serv01 work]# grep -A 2 first grepfile2
first line
second line
third line

• matching two lines before the matching word

[root@RHEL5-Serv01 work]# grep -B 2 third grepfile2
first line
second line
third line

• matching two lines before and after the matching word

[root@RHEL5-Serv01 work]# grep -C 2 third grepfile2
first line
second line
third line
fourth line
fifth line

• showing lines that do not match the search word

[root@RHEL5-Serv01 work]# grep -v line grepfile2

[root@RHEL5-Serv01 work]#

• let's find the file containing our search word

[root@RHEL5-Serv01 work]# ls
grepfile  grepfile1  grepfile2
[root@RHEL5-Serv01 work]# grep -l line grepfile*
grepfile2

•  let's find the line number that containts the search word

[root@RHEL5-Serv01 work]# grep -n line grepfile2

1:first line

2:second line

3:third line

4:fourth line

5:fifth line

6:seventh line

7:eighth line

8:nineth line

9:tenth line

10:ten lines in total contain the word line

GREP USING REGULAR EXPRESSIONS

$ cat file

i am

you are

he is

she is

we are

you are

they are

so what do we do?!

080-9876-9999

ab2354cF

$ grep 'a.e' file

you are

we are

you are

they are

$ grep 'w[a-z]\{2\}t' file(same as "grep w..t file")

so what do we do?!

$grep '[0-9]\{3\}-[0-9]\{4\}-[0-9]\{4\}' file
080-9876-9999