数据流导向

[dai@workPC ~]$ ll / > ~/rootfile

[dai@workPC ~]$ cat rootfile

total 80

lrwxrwxrwx.   1 root root     7 Mar  7  2019 bin -> usr/bin

dr-xr-xr-x.   6 root root  4096 Dec 31 19:36 boot

drwxr-xr-x    2 root root  4096 Mar 12  2019 data

drwxr-xr-x   19 root root  3000 Oct 13 08:27 dev

drwxr-xr-x. 107 root root 12288 Dec 31 19:37 etc

drwxr-xr-x.   4 root root  4096 Dec  1 23:54 home

lrwxrwxrwx.   1 root root     7 Mar  7  2019 lib -> usr/lib

lrwxrwxrwx.   1 root root     9 Mar  7  2019 lib64 -> usr/lib64

drwx------.   2 root root 16384 Mar  7  2019 lost+found

drwxr-xr-x.   2 root root  4096 Apr 11  2018 media

drwxr-xr-x.   2 root root  4096 Apr 11  2018 mnt

drwxr-xr-x.  11 root root  4096 Dec 30 21:16 opt

dr-xr-xr-x  103 root root     0 Oct 13 08:27 proc

dr-xr-x---.  10 root root  4096 Jan  1 12:05 root

drwxr-xr-x   34 root root  1160 Dec 31 19:37 run

lrwxrwxrwx.   1 root root     8 Mar  7  2019 sbin -> usr/sbin

drwxr-xr-x.   2 root root  4096 Apr 11  2018 srv

dr-xr-xr-x   13 root root     0 Jan  1 20:01 sys

drwxrwxrwt.  16 root root 12288 Jan  1 12:53 tmp

drwxr-xr-x.  13 root root  4096 Mar  7  2019 usr

drwxr-xr-x.  19 root root  4096 Mar  7  2019 var

# 标准错误输入，导出到黑洞

# /dev/null  垃圾桶黑洞装置与特殊写法

[dai@workPC /]$ cd root/

-bash: cd: root/: Permission denied

[dai@workPC home]$ cd root/ 2> /home/dai/error1.log

[dai@workPC ~]$ cat error1.log

-bash: cd: root/: No such file or directory

# /dev/null 垃圾桶黑洞装置与特殊写法

[dai@workPC /]$ cd root/ 2> /dev/null        

[dai@workPC /]$

# 将错误和正确信息一起导出文件中, 比如下面的这个例子，如果权限不够的时候，屏幕会输出错误信息

# 这个时候将正确和错误信息都输出到 file_name 这个文件

 find /home -name .bashrc > file_name 2>&1

[dai@workPC ~]$ cat > rootfile

wqe

we2

^C

[dai@workPC ~]$ cat rootfile

wqe

we2

[dai@workPC ~]$

# 下面就是input的用法

# 将一个文件作为另一个文件的输入

[dai@workPC ~]$ cat > rootfile  < ~/.bashrc   # 将.bashrc 文件中的内容导入 rootfile

# 使用关键字给文件插入文字

[dai@workPC ~]$ cat > rootfile << eof

> This is a test

> OK now stop

> eof

[dai@workPC ~]$ cat rootfile

This is a test

OK now stop

# 不考虑指令是否执行成功

# 如果cmd1 正确执行，再执行cmd2；如果cmd1执行失败，则不再执行cmd2

# 如果cmd1 正确执行，不再执行cmd2；如果cmd1执行失败，再执行cmd2