[root@localhost ~]# grep -A 1 "123" /tmp/test/b
12312131231
THIS IS A "TEST"
[root@localhost ~]# grep -B 1 "123" /tmp/test/b
q
12312131231
[root@localhost ~]# grep -C 1 "123" /tmp/test/b
q
12312131231
THIS IS A "TEST"
[root@localhost ~]# grep -c "ab" /tmp/test/b
3
[root@localhost ~]# grep -e "ab" -e "ef" /tmp/test/b
aaabbbccc
abcabc
abcdefg
[root@localhost ~]# grep -i "is" /tmp/test/b
THIS IS A "TEST"
[root@localhost ~]# grep -o "IS" /tmp/test/b
IS
IS
[root@localhost ~]# grep -q "IS" /tmp/test/b
[root@localhost ~]# grep -v "IS" /tmp/test/b
aaabbbccc
abcabc
abcdefg
s
r
q
12312131231