Shell input and output redirection

Standard input: 0 <, << or 0< 0<<

Standard output: 1 >,>> or 1>,1>>

Error Output: 2 2>>,2>

/dev/null 这个设备，是linux 中黑洞设备，什么信息只要输出给这个设备，都会给吃掉 Send standard output, error output to/dev/null $ ls test .sh test1.sh > /dev/null 2>&1&AMP;,&AMP;1 represents the standard output &AMP;2 represents the error output

The//Error output is written directly in the standard output, which is displayed on the terminal screen.

: ~$ Ls-yz 2>&1
Ls:invalid option--' Y '
Try ' ls--help ' for more information.

The error output is output to the standard output, which is displayed on the screen and not written in the fname file.
: ~$ Ls-yz 2>&1 1>fname
Ls:invalid option--' Y '
Try ' ls--help ' for more information.
: ~$ ls
Androidstudioprojects Desktop Documents Downloads examples.desktop fname Music Pictures public Templates USR Videos work
: ~$ Cat FName

The// standard output is written in the fname file, and the error output is output to the standard output, which is the file fname.
: ~$ Ls-yz 1>fname 2>&1
: ~$ ls
Androidstudioprojects Desktop Documents Downloads examples.desktop fname Music Pictures public Templates USR Videos work
: ~$ Cat FName
Ls:invalid option--' Y '
Try ' ls--help ' for more information.

Shell input and output redirection