[Linux Command sorting 8] alias, input/output redirection, pipeline, command connector, command replacement character

Command 1: alias

An alias is used for convenience. If you have a frequently-used command for a long time, you can set an alias to be equivalent. For example, the default alias of LS-Alf is ll.

 

The alias format is as follows:

Alias alias = command

Alias alias = "command combination"

Alias allows you to view the configured aliases

Unalias alias Delete alias

 

Command 2: Input/Output redirection

Output redirection

Input the result of a command to a file.

For example:

Ls-L/ABC>/ABC. MSG Overwrite

Ls-L/ABC>/ABC. MSG append Does Not Overwrite

 

Input redirection

Wall </abc.txt

 

Error output redirection

Ls/ABC 2> ls. Error

If the execution of LS/ABC is normal, it will not be output to LS. Error.

If the LS/ABC execution fails, for example, the ABC directory does not exist, it will be output to LS. Error.

 

Command 3: MPS queue

Use the result of the previous command as the input of the next command.

For example, if you want to view LS-L/etc, but you want to view too much content by page, you can use the pipeline symbol | in series: ls-L/etc | more

You can set multiple MPs queues.

For example, to view the number of init-related files in LS-L/etc, use LS-L/etc | Gret init | WC-L.

 

Command 4: Command Connector

1. execute commands in sequence and connect

Example: whoami; PWD; Date

 

2. After the previous command is successfully executed, the next command will run & connect

Example: Write Mary </love.txt & RM/love.txt

 

3. If the previous command fails to be executed, the next command will be executed. | connection

Example: Write Mary </love.txt | mail Mary/love.txt

 

Command 5: Command replacement character

Use the execution result of one command as the parameter of another command :''

Example: ls-l 'which Touch'