管道及 I/O 重定向

电玩女神 2023-01-04 11:56 146阅读 0赞

##  I/O重定向 ##

#### I/O Redirection ####

标准输入、标准输出、标准错误  
输出重定向及综合案例  
输入重定向及结合案例  
  
标准输入、标准输出、标准错误  
![1479786-20191217151211579-267603737.png][]

file descriptors （FD，文件描述符 或 Process I/O channels）：  
进程使用文件描述符来管理打开的文件  
\[root@CentOS7 ~\]\# ls /proc/$$/fd  
0 1 2 3 4  
  
0, 1, and 2, known as standard input, standard output, and standard error  
![1479786-20191217151237912-1980503856.png][]

输出重定向 (覆盖，追加)  
正确输出： 1> 1>> 等价于 > >>  
错误输出： 2> 2>>  
  
案例1：输出重定向（覆盖）  
\[root@CentOS7 ~\]\# date 1> date.txt  
![1479786-20191217151256919-1623909658.png][]

案例2：输出重定向（追加）  
\[root@CentOS7 ~\]\# date >> date.txt  
![1479786-20191217151314185-1565792659.png][]

案例3：错误输出重定向  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa >list.txt  
ls: 无法访问/aaaaaaaaa: 没有那个文件或目录  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa >list.txt 2>error.txt //重定向到不同的位置  
![1479786-20191217151333733-1588279513.png][]

案例4： 正确和错误都输入到相同位置  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa &>list.txt //混合输出  
![1479786-20191217151353378-848031169.png][]

案例5： 正确和错误都输入到相同位置  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa >list.txt 2>&1 //重定向到相同的位置  
![1479786-20191217151412463-1121577457.png][]

案例6：重定向到空设备/dev/null  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa >list.txt 2>/dev/null //空设备，即将产生的输出丢掉  
\[root@CentOS7 ~\]\# ls /home/ /aaaaaaaaa &>/dev/null //空设备，即将产生的输出丢掉  
![1479786-20191217151450712-1359393612.png][]

**cp /etc/passwd /dev/null ???**  
**cp /etc/passwd /etc/passwd1 2>/dev/null ???**

sudo rm /dev/null  
sudo mknod -m 666 /dev/null c 1 3  
![1479786-20191217151536744-1853104730.png][]

案例7：脚本中使用重定向  
\# vim ping.sh  
\#!/usr/bin/bash  
ping -c1 172.16.120.254 &>/dev/null  
if \[ $? -eq 0 \];then  
echo "up.."  
else  
echo "down.."  
fi  
\# bash ping.sh  
  
案例8：脚本中使用重定向  
\# vim ping2.sh  
\#!/usr/bin/bash  
ping -c1 172.16.120.254 &>/dev/null  
if \[ $? -eq 0 \];then  
echo "172.16.120.254 up.." > /up.txt  
else  
echo "172.16.120.254 down.." >/down.txt  
fi  
\# bash ping2.sh

>new.txt ???  
>/etc/passwd ???  
>/etc ???

输入重定向  
标准输入： < 等价 0<  
案例1：  
\[root@CentOS7 ~\]\# mail -s "ssss" alice //没有改变输入的方向，默认键盘  
111  
222  
333  
^D  
\[root@CentOS7 ~\]\# su - alice  
\[alice@CentOS7 ~\]$ mail  
Mail version 8.1 6/6/93. Type ? for help.  
"/var/spool/mail/alice": 1 message 1 new  
>N 1 root@CentOS7.local Mon Oct 29 14:09 18/657 "ssss"  
&  
  
\[root@CentOS7 ~\]\# mail -s "test01" alice < /etc/hosts //输入重定向，来自于文件  
  
案例2：  
\[root@CentOS7 ~\]\# grep 'root' //没有改变输入的方向，默认键盘，此时等待输入...  
yang sss  
sssrootssss..  
sssrootssss..  
  
\[root@CentOS7 ~\]\# grep 'root' < /etc/passwd  
root:x:0:0:root:/root:/bin/bash  
operator:x:11:0:operator:/root:/sbin/nologin  
  
案例3：  
\[root@CentOS7 ~\]\# dd if=/dev/zero of=/file1.txt bs=1M count=2  
\[root@CentOS7 ~\]\# dd </dev/zero >/file2.txt bs=1M count=20  
  
案例4：mysql表结构导入  
\[root@CentOS7 ~\]\# mysql -uroot -p123 < bbs.sql  
  
案例5：at  
\[root@CentOS7 ~\]\# at now +5 min  
at> useradd yang99  
at> <EOT>  
job 1 at 2015-06-09 11:57  
  
\[root@CentOS7 ~\]\# vim at.txt  
sudo useradd yang100  
sudo useradd yang102  
\[root@CentOS7 ~\]\# at now +2 min < at.txt  
job 2 at 2015-06-09 11:55

sudo: sorry, you must have a tty to run sudo  
sudo: sorry, you must have a tty to run sudo

综合案例1: 利用重定向建立多行的文件  
\[root@CentOS7 ~\]\# echo "111" > file1.txt  
\[root@CentOS7 ~\]\# cat file1.txt  
111  
  
\[root@CentOS7 ~\]\# cat >file2.txt  
111  
222  
333  
444  
^D  
\[root@CentOS7 ~\]\# cat file2.txt

请问：file2.txt有几行？

\[root@CentOS7 ~\]\# cat >>file3.txt  
aaa  
bbb  
ccc  
ddd  
^D  
\[root@CentOS7 ~\]\# cat file3.txt

请问：file3.txt有几行？

\[root@CentOS7 ~\]\# cat >file4 <<EOF  
> 111  
> 222  
> 333  
> EOF  
\[root@CentOS7 ~\]\# cat file4  
111  
222  
333  
  
  
综合案例2: 脚本中利用重定向打印消息  
\[root@CentOS7 ~\]\# vim yang.sh  
\#!/usr/bin/bash  
cat <<-EOF  
\+------------------------------------------------+  
| |  
| ====================== |  
| 虚拟机基本管理centos |  
| by CentOS7 |  
| ====================== |  
| 1. 安装虚拟机 |  
| 2. 重置所有Linux虚拟机 |  
| 3. 重置Windows虚拟机 |  
| 4. 重置Windows虚拟机 \[完全\] |  
| 5. 重置指定的虚拟机 |  
| q. 退出管理程序 |  
| |  
\+------------------------------------------------+  
EOF  
  
  
综合案例3  
\[root@CentOS7 ~\]\# ls; date &>/dev/null  
  
\[root@CentOS7 ~\]\# ls &>/dev/null; date &>/dev/null  
  
\[root@CentOS7 ~\]\# (ls; date) &>/dev/null  
  
\[root@CentOS7 ~\]\# (while :; do date; sleep 2; done) &>date.txt  
  
\[root@CentOS7 ~\]\# (while :; do date; sleep 2; done) &>date.txt &  
\[1\] 6595  
\[root@CentOS7 ~\]\# tailf date.txt  
Tue Apr 12 22:04:32 CST 2016  
Tue Apr 12 22:04:34 CST 2016  
Tue Apr 12 22:04:36 CST 2016  
Tue Apr 12 22:04:38 CST 2016  
Tue Apr 12 22:04:40 CST 2016  
Tue Apr 12 22:04:42 CST 2016  
Tue Apr 12 22:04:44 CST 2016  
Tue Apr 12 22:04:46 CST 2016  
Tue Apr 12 22:04:48 CST 2016  
  
\[root@CentOS7 ~\]\# jobs  
\[1\]+ Running ( while :; do  
date; sleep 2;  
done ) &>date.txt &  
\[root@CentOS7 ~\]\# kill %1  
\[root@CentOS7 ~\]\# jobs  
  
\[root@CentOS7 ~\]\# (./configure && make && make install) &>/dev/null  
  
扩展点：subshell  
\[root@CentOS7 ~\]\# (umask 777; touch file8888)  
\[root@CentOS7 ~\]\#  
\[root@CentOS7 ~\]\# ll file8888  
\---------- 1 root root 0 Apr 12 22:11 file8888  
\[root@CentOS7 ~\]\#  
\[root@CentOS7 ~\]\# umask  
0022

## 进程管道 Piping ##

• Use redirection characters to control output to files.  
• Use piping to control output to other programs.  
  
files: > 2> file1.txt /dev/pts/2 /dev/tty1 /dev/null /dev/sda  
programs: |  
  
进程管道  
用法：command1 | command2 |command3 |...  
![1479786-20191217151708547-1248120367.png][]

\[root@CentOS7 ~\]\# ll /dev/ |less  
\[root@CentOS7 ~\]\# ps aux |grep 'sshd'  
\[root@CentOS7 ~\]\# rpm -qa |grep 'httpd' //查询所有安装的软件包，过滤包含httpd的包  
\[root@CentOS7 ~\]\# yum list |grep 'httpd'  
  
案例1：将/etc/passwd中的用户按UID大小排序  
\[root@CentOS7 ~\]\# sort -t":" -k3 -n /etc/passwd //以: 分隔，将第三列按字数升序  
\[root@CentOS7 ~\]\# sort -t":" -k3 -n /etc/passwd -r //逆序  
\[root@CentOS7 ~\]\# sort -t":" -k3 -n /etc/passwd |head  
\-t 指定字段分隔符--field-separator  
\-k 指定列  
\-n 按数值  
  
案例2：统计出最占CPU的5个进程  
\[root@CentOS7 ~\]\# ps aux --sort=-%cpu |head -6  
  
案例3：统计当前/etc/passwd中用户使用的shell类型  
思路：取出第七列（shell） | 排序（把相同归类）| 去重  
\[root@CentOS7 ~\]\# awk -F: '\{print $7\}' /etc/passwd  
\[root@CentOS7 ~\]\# awk -F: '\{print $7\}' /etc/passwd |sort  
\[root@CentOS7 ~\]\# awk -F: '\{print $7\}' /etc/passwd |sort |uniq  
\[root@CentOS7 ~\]\# awk -F: '\{print $7\}' /etc/passwd |sort |uniq -c  
131 /bin/bash  
1 /bin/sync  
1 /sbin/halt  
63 /sbin/nologin  
1 /sbin/shutdown  
\-F: 指定字段分隔符  
$7 第七个字段  
  
案例4： 统计网站的访问情况 top 20  
思路： 打印所有访问的连接 | 过滤访问网站的连接 | 打印用户的IP | 排序 | 去重  
\[root@CentOS7 ~\]\# ss -an |grep :80 |awk -F":" '\{print $8\}' |sort |uniq -c  
4334 192.168.0.66  
1338 192.168.10.11  
1482 192.168.10.125  
44 192.168.10.183  
3035 192.168.10.213  
375 192.168.10.35  
362 192.168.10.39  
\[root@CentOS7 ~\]\# ss -an |grep :80 |awk -F":" '\{print $8\}' |sort |uniq -c |sort -k1 -rn |head -n 20  
  
案例5： 打印当前所有IP  
\[root@CentOS7 ~\]\# ip addr |grep 'inet ' |awk '\{print $2\}' |awk -F"/" '\{print $1\}'  
127.0.0.1  
192.168.2.115  
  
案例6：打印根分区已用空间的百分比（仅打印数字）  
\[root@CentOS7 ~\]\# df -P |grep '/$' |awk '\{print $5\}' |awk -F"%" '\{print $1\}'  
  
  
tee管道  
![1479786-20191217151728189-739939030.png][]

\[root@CentOS7 ~\]\# ip addr |grep 'inet ' |tee ip.txt |awk -F"/" '\{print $1\}' |awk '\{print $2\}'  
127.0.0.1  
172.16.60.1  
\[root@CentOS7 ~\]\# cat ip.txt  
inet 127.0.0.1/8 scope host lo  
inet 172.16.60.1/24 brd 172.16.60.255 scope global eth0  
  
  
\[root@CentOS7 ~\]\# ip addr |grep 'inet ' |tee -a ip.txt |awk -F"/" '\{print $1\}' |awk '\{print $2\}'  
127.0.0.1  
172.16.60.1  
  
\[root@CentOS7 ~\]\# date |tee date.txt  
Sat Mar 11 10:22:31 CST 2017

## 参数传递 Xargs ##

awk sed grep sort uniq less more xargs  
xargs: ls cp rm  
  
案例1  
\[root@localhost ~\]\# touch /home/file\{1..5\}  
  
\[root@localhost ~\]\# vim files.txt  
/home/file1  
/home/file2  
/home/file3  
/home/file4  
/home/file5  
  
\[root@localhost ~\]\# cat files.txt |ls -l  
\[root@localhost ~\]\# cat files.txt |rm -rvf  
  
cont.  
\[root@localhost ~\]\# cat files.txt |xargs ls -l  
\-rw-r--r--. 1 root root 0 Mar 11 10:35 /home/file1  
\-rw-r--r--. 1 root root 0 Mar 11 10:35 /home/file2  
\-rw-r--r--. 1 root root 0 Mar 11 10:35 /home/file4  
\-rw-r--r--. 1 root root 0 Mar 11 10:35 /home/file5  
  
\[root@localhost ~\]\# cat files.txt |xargs rm -rvf  
removed ‘/home/file1’  
removed ‘/home/file2’  
removed ‘/home/file4’  
removed ‘/home/file5’  
  
案例2  
\[root@localhost ~\]\# touch /home/file\{1..5\}  
\[root@localhost ~\]\# cat files.txt |xargs -I \{\} ls -l \{\}  
\-rw-r--r--. 1 root root 0 Mar 11 10:40 /home/file1  
\-rw-r--r--. 1 root root 0 Mar 11 10:40 /home/file2  
\-rw-r--r--. 1 root root 0 Mar 11 10:40 /home/file4  
\-rw-r--r--. 1 root root 0 Mar 11 10:40 /home/file5  
  
\[root@localhost ~\]\# cat files.txt |xargs -I \{\} cp -rvf \{\} /tmp  
‘/home/file1’ -> ‘/tmp/file1’  
‘/home/file2’ -> ‘/tmp/file2’  
‘/home/file4’ -> ‘/tmp/file4’  
‘/home/file5’ -> ‘/tmp/file5’  
  
\[root@localhost ~\]\# cat files.txt |xargs -I YANG cp -rvf YANG /var/tmp  
‘/home/file1’ -> ‘/var/tmp/file1’  
‘/home/file2’ -> ‘/var/tmp/file2’  
‘/home/file4’ -> ‘/var/tmp/file4’  
‘/home/file5’ -> ‘/var/tmp/file5’  
  
案例3  
\[root@localhost ~\]\# find /etc -iname "\*ifcfg\*" |xargs -I \{\} cp -rf \{\} /tmp

[1479786-20191217151211579-267603737.png]: /images/20221119/56c988007b984310bdd403ec8bf3330d.png
[1479786-20191217151237912-1980503856.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151237912-1980503856.png
[1479786-20191217151256919-1623909658.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151256919-1623909658.png
[1479786-20191217151314185-1565792659.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151314185-1565792659.png
[1479786-20191217151333733-1588279513.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151333733-1588279513.png
[1479786-20191217151353378-848031169.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151353378-848031169.png
[1479786-20191217151412463-1121577457.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151412463-1121577457.png
[1479786-20191217151450712-1359393612.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151450712-1359393612.png
[1479786-20191217151536744-1853104730.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151536744-1853104730.png
[1479786-20191217151708547-1248120367.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151708547-1248120367.png
[1479786-20191217151728189-739939030.png]: https://img2018.cnblogs.com/i-beta/1479786/201912/1479786-20191217151728189-739939030.png