Redirect and piping and tr tee commands

1. Redirect

Input redirection is to overwrite or append the execution result or string of the command to a file

Command: > (overwrite) > > (append)

There are three types of linux output:

Standard input 0: keyboard input

Standard output 1: default output to terminal window

Error output 2: default output to terminal window

According to the output result, the output is redirected to the file:

Overwrite correct output and redirect to file

2 > overwrite error output redirected to file

2 > > append error output redirects to file

& > overwrite all output redirects to files

Append all output redirects to the file

> file > & 1 overwrites all output redirects to files

Merge multiple programs and redirect to a file

(ls;pwd) > F1 multiple command redirection

> the contents of the file will be overwritten

Set-C: it is forbidden to overwrite existing files, but you can add mandatory overrides: > |

Set + C: allow override

> > add content on the basis of the original content

Input redirection

Command:

< 将文件中的内容传递给命令执行 cat < /etc/fstab cat &1 |Command2 Command1 |& Command2 [root@localhost ~]# xecho asdfasdf 2>

& 1 | tr "Amurz" 'Amurz'

BASH: XECHO: command not found.

A similar command is: 'ECHO'

3. Tr command

Options:

-d info: delete information matching to info

[root@localhost ~] # echo abcdefg | tr-d abc

Defg

-c info: complement, except for info

[root@localhost ~] # echo abcdefg | tr-cd abc

Abc [root@localhost ~] #

-s info: remove the duplicate info and keep one

[root@localhost ~] # echo aabbbcc | tr-s ab

Abcc

'AmurZ'aMuzhuang: convert all uppercase characters to lowercase

[root@localhost ~] # echo aabbbcc | tr'amurz''AmurZ'

AABBBCC

-t info1 info2: replace by bit matching. Bits that do not match are not replaced.

[root@localhost ~] # echo abcdef | tr-t 'abcde'' 11'

11cdef

Info1 info2: replace all the information in info1 with the last bit of info2 that matches.

[root@localhost ~] # echo abcdef | tr 'abcde'' 11'

11111f

4. Tee command

Transfer ancient information from the upper level of the pipeline, save it to a file, and display the wound on the screen.

Ls | tee / testdir/ls.log | tr'amurz 'Amurz' > / tmp/who.out

The default is override-an is appended