Pipelines and redirection

Redirection of input and output. standard Input Device: Corresponding Device File: devstdin, 0-device descriptor KEYBOARD standard output device: devstdout, 1MONITOR error output: devstderr, 2MONITOR redirection; input redirection: Indicates output redirection: overwrite, overwrite the original content, and append redirection e.

Redirection of input/output.

Standard input device:

Corresponding device file:

/Dev/stdin, 0-device descriptor KEYBOARD

Standard output device:

/Dev/stdout, 1 MONITOR

Error output:

/Dev/stderr, 2 MONITOR

Redirection;

Input redirection: <indicates

Output redirection:> overwrites the original content.

> Indicates append redirection.

Echo "------------------"> .......

Error output: 2>

(The output stream and the error output stream are different data streams)

Merge error standard output stream &> but not supported &>

To avoid mistakes:

 Set-C. Existing files cannot be overwritten.

, Disable overwrite redirection

You can use "> |" to force overwrite redirection.

Example:Ls/Var>/File2>/file2 correct information error messages are stored separately

Pipeline: "|"

COMMAND | COMMAND

FirstCommandAs the input of the next command,

Example: echo "123456" |Passwd-- Stdin rEdHat -- stdin