shell脚本的简单练习

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[root@localhost shell]# cp /etc/passwd ./

[root@localhost shell]# head -1 passwd
root:x:0:0:root:/root:/bin/bash
[root@localhost shell]# head -1 passwd | awk -F: '{print $3,$6,$7}'
0 /root /bin/bash
[root@localhost shell]# head -1 passwd | awk -F: '{print $0}'
root:x:0:0:root:/root:/bin/bash

[root@localhost shell]# head -1 passwd | awk -F: '{print $3":"$6":"$7}'
0:/root:/bin/bash
[root@localhost shell]# head -1 passwd
root:x:0:0:root:/root:/bin/bash
[root@localhost shell]# head -1 passwd | cut -d: -f2
x
[root@localhost shell]# head -1 passwd | cut -d: -f3,6,7
0:/root:/bin/bash
[root@localhost shell]# head -1 passwd | cut -d: -f3,6,7| tr ":" " "
0 /root /bin/bash
[root@localhost shell]# awk 'BEGIN{FS=":"}/^root/{print $1}' passwd
root

[root@localhost shell]# awk -F: '/^root/{print $1}' passwd
root

[root@localhost shell]# awk -F: 'BEGIN{print"********"}/^root/ {print $1,"a",$7} END {print "======"}' passwd
********
root a /bin/bash
======

[root@localhost shell]# awk -F: '{if ($7~"/bin/bash") print
$0}' passwd
root:x:0:0:root:/root:/bin/bash

[root@localhost shell]# awk -F: '{if ($7~"/bin/bash") print
$1;else print $2}' passwd
root
x
x

[root@localhost shell]# cat test.txt
aa bb a b aaa aaaa bbbb bb
ab ab abc bbb bbbb bb aa
aa aaa aaa aaaa aaaaa bbbbb
bb bbab ab abbb abbab aa
bbbb bbb bbb bbbbb bbbbb aab
aa bb
ab aabb

[root@localhost shell]# awk 'gsub("aa","bb"){print $0}' test.txt
bb bb a b bba bbbb bbbb bb
ab ab abc bbb bbbb bb bb
bb bba bba bbbb bbbba bbbbb
bb bbab ab abbb abbab bb
bbbb bbb bbb bbbbb bbbbb bbb
bb bb
ab bbbb

[root@localhost shell]# awk 'gsub("bb","cc")' test.txt
aa cc a b aaa aaaa cccc cc
ab ab abc ccb cccc cc aa
aa aaa aaa aaaa aaaaa ccccb
cc ccab ab accb accab aa
cccc ccb ccb ccccb ccccb aab
aa cc
ab aacc

[root@localhost shell]# awk 'gsub("\\ybb\\y","cc")' test.txt
aa cc a b aaa aaaa bbbb cc
ab ab abc bbb bbbb cc aa
cc bbab ab abbb abbab aa
aa cc

awk 'BEGIN {
for(j=1;j<=12;j++)
{ flag=0;
printf "\n%d月份\n",j;
for(i=1;i<=31;i++)
{
if (j==2&&i>28) flag=1;
if ((j==4||j==6||j==9||j==11)&&i>30) flag=1;
if (flag==0) {printf "%02d%02d ",j,i}
}
}
}'

1月份
0101 0102 0103 0104 0105 0106 0107 0108 0109 0110 0111 0112 0113 0114 0115 0116 0117 0118 0119 0120 0121 0122 0123 0124 0125 0126 0127 0128 0129 0130 0131
2月份
0201 0202 0203 0204 0205 0206 0207 0208 0209 0210 0211 0212 0213 0214 0215 0216 0217 0218 0219 0220 0221 0222 0223 0224 0225 0226 0227 0228
3月份

……………………………………………………

[root@localhost shell]# sed -n /root/p passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin
[root@localhost shell]#

[root@localhost shell]# awk '{print $0}' fstab
LABEL=/ / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
LABEL=SWAP-sda2 swap swap defaults 0 0
##

[root@localhost shell]# awk '{print $0}' fstab | sed '2,$'d
LABEL=/ / ext3 defaults 1 1

[root@localhost shell]# cat test.txt
aa bb a b aaa aaaa bbbb bb
ab ab abc bbb bbbb bb aa
aa aaa aaa aaaa aaaaa bbbbb
bb bbab ab abbb abbab aa
bbbb bbb bbb bbbbb bbbbb aab
aa bb
ab aabb

[root@localhost shell]# sed -i s/aa/ABC/g test.txt
[root@localhost shell]# cat test.txt
ABC bb a b ABCa ABCABC bbbb bb
ab ab abc bbb bbbb bb ABC
ABC ABCa ABCa ABCABC ABCABCa bbbbb
bb bbab ab abbb abbab ABC
bbbb bbb bbb bbbbb bbbbb ABCb
ABC bb
ab ABCbb

[root@localhost shell]# sed /aa/'a S' test.txt
aa bb a b aaa aaaa bbbb bb
S
ab ab abc bbb bbbb bb aa
S
aa aaa aaa aaaa aaaaa bbbbb
S
bb bbab ab abbb abbab aa
S
bbbb bbb bbb bbbbb bbbbb aab
S
aa bb
S
ab aabb
S

[root@localhost shell]# sed 3'a abc' test.txt 在第三行后面添加abc
aa bb a b aaa aaaa bbbb bb
ab ab abc bbb bbbb bb aa
aa aaa aaa aaaa aaaaa bbbbb
abc
bb bbab ab abbb abbab aa
bbbb bbb bbb bbbbb bbbbb aab
aa bb
ab aabb

[root@localhost shell]# cat 3.sh

对比一下echo和EOF输出的格式。