Linux-重定向与管道

Linux-重定向与管道

系统设定：

默认输入设备      // 标准输入，STDIN，0  （键盘）

默认输出设备      // 标准输出，STDOUT，1 （显示器）

标准错误输出      // 标准错误，STDERR，2 （显示器）

I/O重定向：

>：覆盖输出(默认是1>，可省略1)

[root@localhost ~]# ls
anaconda-ks.cfg
[root@localhost ~]# ls > abc
[root@localhost ~]# cat abc
abc
anaconda-ks.cfg
[root@localhost ~]# ls > abc
[root@localhost ~]# ls > abc
[root@localhost ~]# ls > abc
[root@localhost ~]# cat abc
abc
anaconda-ks.cfg

>>：追加输出

[root@localhost ~]# ls >> abc
[root@localhost ~]# cat abc
abc
anaconda-ks.cfg
abc
anaconda-ks.cfg
[root@localhost ~]# ls >> abc
[root@localhost ~]# ls >> abc
[root@localhost ~]# ls >> abc
[root@localhost ~]# cat abc
abc
anaconda-ks.cfg
abc
anaconda-ks.cfg
abc
anaconda-ks.cfg
abc
anaconda-ks.cfg
abc
anaconda-ks.cfg

2>：重定向错误输出

[root@localhost ~]# ls
abc  anaconda-ks.cfg  def
[root@localhost ~]# ls abc def suibiandayigewenjian
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc  def
[root@localhost ~]# ls abc def suibiandayigewenjian > stdout 2> stderr
[root@localhost ~]# cat stdout
abc
def
[root@localhost ~]# cat stderr
ls: cannot access 'suibiandayigewenjian': No such file or directory

2>> ：追加重定向错误输出

[root@localhost ~]# ls abc def suibiandayigewenjian 2>> stderr
abc  def
[root@localhost ~]# ls abc def suibiandayigewenjian 2>> stderr
abc  def
[root@localhost ~]# ls abc def suibiandayigewenjian 2>> stderr
abc  def
[root@localhost ~]# cat stderr
ls: cannot access 'suibiandayigewenjian': No such file or directory
ls: cannot access 'suibiandayigewenjian': No such file or directory
ls: cannot access 'suibiandayigewenjian': No such file or directory
ls: cannot access 'suibiandayigewenjian': No such file or directory

&> ：覆盖重定向标准输出或错误输出至同一个文件

[root@localhost ~]# ls abc def suibiandayigewenjian > stderr
ls: cannot access 'suibiandayigewenjian': No such file or directory
[root@localhost ~]# cat stderr
abc										// 错误输出没写进去需要用&>
def
[root@localhost ~]# ls abc def suibiandayigewenjian &> stderr
[root@localhost ~]# cat stderr
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc
def

&>>：追加重定向标准输出或错误输出至同一个文件

[root@localhost ~]# ls abc def suibiandayigewenjian &>> stderr
[root@localhost ~]# ls abc def suibiandayigewenjian &>> stderr
[root@localhost ~]# ls abc def suibiandayigewenjian &>> stderr
[root@localhost ~]# cat stderr 
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc
def
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc
def
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc
def
ls: cannot access 'suibiandayigewenjian': No such file or directory
abc
def

< ：输入重定向

[root@localhost ~]# ls > abc
[root@localhost ~]# cat abc
abc
anaconda-ks.cfg
def
stderr
stdout
[root@localhost ~]# cat > io < abc				// 把abc的内容写进io
[root@localhost ~]# cat io
abc
anaconda-ks.cfg
def
io
stderr
stdout

<<：Here Document

从标准输入中读入，直到遇到分界符停止

[root@localhost ~]# cat > yqh <<EOF
> wo
> zai
> xie
> zuo
> ye
> EOF
[root@localhost ~]# cat yqh
wo
zai
xie
zuo
ye

管道符 "|":

前一个命令的输出，作为后一个命令的输入。最后一个命令会在当前shell进程 的子shell进程中执行

管道符可以有多个，例：命令1 | 命令2 | 命令3 | ...

[root@localhost ~]# ls |grep 'g$'
anaconda-ks.cfg
bbg
ccg
ffg
[root@localhost ~]# ls |grep '^a'|grep 'g$'
anaconda-ks.cfg

tee

从标准输入读取数据，输出一份到屏幕上，一份保存到文件

[root@localhost ~]# echo 'hello world' | tee Linux
hello world
[root@localhost ~]# cat Linux 
hello world