1、 参数：
-I ：忽略大小写
-c ：打印匹配的行数
-l ：从多个文件中查找包含匹配项
-v ：查找不包含匹配项的行
-n：打印包含匹配项的行和行标

2、RE（正则表达式）
\ 忽略正则表达式中特殊字符的原有含义
^ 匹配正则表达式的开始行
$ 匹配正则表达式的结束行
\< 从匹配正则表达式的行开始
\> 到匹配正则表达式的行结束
[ ] 单个字符；如[A] 即A符合要求
[ - ] 范围 ；如[A-Z]即A，B，C一直到Z都符合要求
. 所有的单个字符
* 所有字符，长度可以为0

3、举例
# ps -ef | grep in.telnetd
root 19955 181 0 13:43:53 ? 0:00 in.telnetd

# more size.txt size文件的内容
b124230
b034325

# more size.txt | grep '[a-b]' 范围 ；如[A-Z]即A，B，C一直到Z都符合要求
b124230
b044525

# more size.txt | grep '[a-b]'*
b124230
b034325

# more size.txt | grep 'b' 单个字符；如[A] 即A符合要求
b124230
b034325

# more size.txt | grep '[bB]'
b124230
b034325
b103303

# grep 'root' /etc/group
root::0:root
bin::2:root,bin,daemon
sys::3:root,bin,sys,adm
adm::4:root,adm,daemon
uucp::5:root,uucp
mail::6:root
tty::7:root,tty,adm
lp::8:root,lp,adm
nuucp::9:root,nuucp
daemon::12:root,daemon

# grep '^root' /etc/group 匹配正则表达式的开始行
root::0:root

# grep 'uucp' /etc/group
uucp::5:root,uucp
nuucp::9:root,nuucp

# grep '\<uucp' /etc/group
uucp::5:root,uucp

# grep 'root$' /etc/group 匹配正则表达式的结束行
root::0:root
mail::6:root

# more size.txt | grep -i 'b1..*3' -i ：忽略大小写
b124230
b103303
B103303

# more size.txt | grep -iv 'b1..*3' -v ：查找不包含匹配项的行

b034325
a081016

# more size.txt | grep -in 'b1..*3'
1:b124230

# grep '$' /etc/init.d/nfs.server | wc -l
128
# grep '\$' /etc/init.d/nfs.server | wc –l 忽略正则表达式中特殊字符的原有含义

15
# grep '\$' /etc/init.d/nfs.server
case "$1" in
>/tmp/sharetab.$$
[ "x$fstype" != xnfs ] &&

# more size.txt

the test file
their are files
The end

# grep 'the' size.txt
the test file
their are files

# grep '\<the' size.txt
the test file
their are files

# grep 'the\>' size.txt
the test file

# grep '\<the\>' size.txt
the test file

# grep '\<[Tt]he\>' size.txt
the test file