linux命令基础知识 管道流,linux基础知识-I/O重定向,管道(示例代码)

系统设定

默认输出设备：标准输出，STDOUT, 1

默认输入设备：标准输入, STDIN, 0

标准错误输出：STDERR, 2

标准输入：键盘

标准输出和错误输出：显示器

I/O重定向：

Linux:

>: 覆盖输出

[[email protected] ~]# ll /var/ > /tmp/var.out

[[email protected] ~]# cat /tmp/var.out

total 76

drwxr-xr-x.  2 root root 4096 Jun 21  2015 account

drwxr-xr-x. 13 root root 4096 Jun 21  2015 cache

drwxr-xr-x.  2 root root 4096 Jun 21  2015 crash

drwxr-xr-x.  3 root root 4096 Jun 21  2015 db

drwxr-xr-x.  3 root root 4096 Jun 21  2015 empty

drwxr-xr-x.  2 root root 4096 Jun 28  2011 games

#

# /etc/fstab

# Created by anaconda on Sun Jun 21 02:15:00 2015

#

# Accessible filesystems, by reference, are maintained under ‘/dev/disk‘

# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info

#

UUID=57d85756-7680-4c7c-9125-6ad67dae2c45 /                       ext4    defaults        1 1

UUID=2622a4b4-ddc9-47a3-aa2b-f06bc9bec085 /boot                   ext4    defaults        1 2

UUID=33d94759-fa01-4c4f-b4ac-bf3a1fe5e84f swap                    swap    defaults        0 0

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

>>：追加输出

2>: 重定向错误输出

[[email protected] ~]# ls /varr > /tmp/var2.out

ls: cannot access /varr: No such file or directory

[[email protected] ~]# ls /varr 2> /tmp/var2.out

[[email protected] ~]# cat /tmp/var2.out

ls: cannot access /varr: No such file or directory

[[email protected] ~]#

2>>: 追加方式

&>: 重定向标准输出或错误输出至同一个文件

[[email protected] ~]# ls /var6 &> /tmp/var3.out

[[email protected] ~]# cat /tmp/var3.out

ls: cannot access /var6: No such file or directory

[[email protected] ~]# ls /var &> /tmp/var3.out

[[email protected] ~]# cat /tmp/var3.out

account

cache

crash

db

empty

输入重定向

[[email protected] ~]# tr ‘a-z‘ ‘A-Z‘ < /etc/fstab

#

# /ETC/FSTAB

# CREATED BY ANACONDA ON SUN JUN 21 02:15:00 2015

#

# ACCESSIBLE FILESYSTEMS, BY REFERENCE, ARE MAINTAINED UNDER ‘/DEV/DISK‘

# SEE MAN PAGES FSTAB(5), FINDFS(8), MOUNT(8) AND/OR BLKID(8) FOR MORE INFO

#

UUID=57D85756-7680-4C7C-9125-6AD67DAE2C45 /                       EXT4    DEFAULTS        1 1

UUID=2622A4B4-DDC9-47A3-AA2B-F06BC9BEC085 /BOOT                   EXT4    DEFAULTS        1 2

UUID=33D94759-FA01-4C4F-B4AC-BF3A1FE5E84F SWAP                    SWAP    DEFAULTS        0 0

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

[[email protected] ~]#

<

[[email protected] ~]# cat << END

> the first line

> the second line

> END

the first line

the second line

[[email protected] ~]#

从键盘中读入数据，并保存在文档中

cat >> /tmp/myfile.txt << EOF

[[email protected] ~]# cat >> /tmp/myfile.txt << EOF

> the first line

> the second line

> EOF

[[email protected] ~]# cat /tmp/myfile.txt

the first line

the second line

[[email protected] ~]#

管道：前一个命令的输出，作为后一个命令的输入

命令1 | 命令2 | 命令3 | ...

[[email protected] ~]# echo "hello,world" | tr ‘a-z‘ ‘A-Z‘

HELLO,WORLD

[[email protected] ~]#

[[email protected] ~]# echo "redhat" | passwd --stdin hive

Changing password for user hive.

passwd: all authentication tokens updated successfully.

[[email protected] ~]#

同时输出到屏幕和文件中

[[email protected] ~]# echo "hello,world" | tee /tmp/hello.out

hello,world

[[email protected] ~]# cat /tmp/hello.out

hello,world

[[email protected] ~]#

统计文件行数

[[email protected] ~]# wc -l /etc/passwd

32 /etc/passwd

[[email protected] ~]# wc -l /etc/passwd | cut -d‘ ‘ -f1

32

[[email protected] ~]#

练习：

1、统计/usr/bin/目录下的文件个数；

# ls /usr/bin | wc -l

2、取出当前系统上所有用户的shell，要求，每种shell只显示一次，并且按顺序进行显示；

# cut -d: -f7 /etc/passwd | sort -u

3、思考：如何显示/var/log目录下每个文件的内容类型？

4、取出/etc/inittab文件的第6行；

# head -6 /etc/inittab | tail -1

5、取出/etc/passwd文件中倒数第9个用户的用户名和shell，显示到屏幕上并将其保存至/tmp/users文件中；

# tail -9 /etc/passwd | head -1 | cut -d: -f1,7 | tee /tmp/users

6、显示/etc目录下所有以pa开头的文件，并统计其个数；

# ls -d /etc/pa* | wc -l

7、不使用文本编辑器，将alias cls=clear一行内容添加至当前用户的.bashrc文件中；

# echo "alias cls=clear" >> ~/.bashrc