系統設定

默認輸出設備：標準輸出，STDOUT, 1

默認輸入設備：標準輸入, STDIN, 0

標準錯誤輸出：STDERR, 2

標準輸入：鍵盤

標準輸出和錯誤輸出：顯示器

I/O重定向：

Linux:

>: 覆蓋輸出

[[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

>>：追加輸出

2>: 重定向錯誤輸出

[[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

&>: 重定向標準輸出或錯誤輸出至同一個文件

[[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

輸入重定向

[[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] ~]#

從鍵盤中讀入數據，并保存在文檔中

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：前一個命令的輸出，作為后一個命令的輸入

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] ~]#

同時輸出到屏幕和文件中

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

hello,world

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

hello,world

[[email?protected] ~]#

統計文件行數

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

32 /etc/passwd

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

32

[[email?protected] ~]#

練習：

1、統計/usr/bin/目錄下的文件個數；

# ls /usr/bin | wc -l

2、取出當前系統上所有用戶的shell，要求，每種shell只顯示一次，并且按順序進行顯示；

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

3、思考：如何顯示/var/log目錄下每個文件的內容類型？

4、取出/etc/inittab文件的第6行；

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

5、取出/etc/passwd文件中倒數第9個用戶的用戶名和shell，顯示到屏幕上并將其保存至/tmp/users文件中；

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

6、顯示/etc目錄下所有以pa開頭的文件，并統計其個數；

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

7、不使用文本編輯器，將alias cls=clear一行內容添加至當前用戶的.bashrc文件中；

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

總結

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