I/O redirection

Program: Instruction + Data

Data entry: Interactive, file, process

Data output: Monitors, files, processes

Standard input (stdin): 0, keyboard

Standard Output (stdout): 1, monitor

Error Output (stderr): 2, monitor

The normal output and error output are two different data streams;

Redirect:

Output redirection: , >>

COMMAND> new_position: overwrite redirect, will empty the file data ;

CAUTION: hazardous operation; To turn off this feature, you can use the set-c " , the opposite action is "set+c"

COMMAND>> new_position: Follow-up orientation , new data will be appended to the original file data;

Error Output redirection: 2>, 2>>

Command2> Err_output Overwrite the contents of the file

command2>> err_output appended to file data

Two output data streams are also directed :

Method One:

COMMAND> out_file 2>&1

COMMAND>> out_file 2>&1

Method Two:

COMMAND&> out_file

COMMAND&>> out_file

Enter redirection:

command< new_in

TR Command :

Tr[option] ... SET1 [SET2]

put the output data in the each character in the SET1 is correspondingly replaced by each character of the SET2;

-D: Deletes the data that appears in the input stream that belong to each corresponding character of the SET1;

COMMAND << EOF [EOF represents end of File]

[[email protected] tmp]# cat << EOF >abc.txt> I am lx> Hello world> eof> eof[[email protected] tmp]# Cat abc.txt I am lxhello worldeof

REDIRECT content output from input redirection to in the Abc.txt file, EOF can be substituted with any string, case-sensitive

Pipeline: |

put The output of COMMAND1 as the input of COMMAND2, and then the output of COMMAND2 as the input of COMMAND3, etc. .

command1| COMMAND2 | COMMAND3 | ...

Multi-Channel output:

command| Tee/path/to/somefile

Tee Command : The standard input is displayed in the standard output and saved to the file xx, if xx file does not exist is created, the existence will overwrite;

[-A]: append to the back of the file , rather than covering

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I/O redirection