Linux input/Output REDIRECT usage __linux

1, Linux standard input and output

The traditional Linux standard input and output devices are mainly keyboards and monitors, which are described in detail in the following table.

linux standard input Output
device	device file name	file descriptor	type	symbol for
keyboard	/dev/stdin	0 (the default is the keyboard, which is the output of a file or other command 0 o'clock)	standard input	<<	/tr>
monitor	/dev/stdout	1 (default is screen, 1 o'clock is file)	standard output	>>
Monitor	/dev/stderr	2 (default is screen, 2 o'clock is file) /td>	standard error Output	2>	2>>

Note: One of the > says: Cover the contents of the original document;

Two > that is >> : Append to the contents of the original file. 2. Linux output redirection

Output redirection: Changes the input source and the output location of the program running.

The main applicable methods are shown in the following table:

Output redirection
Type	Symbol	Function
Standard output redirection	Commands > Documents	To overwrite the correct output of a command to a specified file or device
Commands >> Documents	To output the correct output of a command to a specified file or device in an append manner
Standard Error Output redirection	Error command 2> file	To overwrite the error output of a command to a specified file or device
Error command 2>> file	Outputs the error output of a command to a specified file or device in an append mode
Correct/error output is saved at the same time	Command > File 2>&1	Save the correct output and error output of the command to the same file in the Overwrite mode
Command >> file 2>&1	Save the correct output and error output of the command to the same file in the Append mode
Commands &> Documents	Save the correct output and error output of the command to the same file in the Overwrite mode
Commands &>> Documents	Save the correct output and error output of the command to the same file in the Append mode
Command >> file 1 2> file 2	In append mode, save the correct output of the command in file 1, and overwrite the error output of the command to file 2.

3. Input redirect

Input redirection
Type	Symbol	Function
Standard input	Command < file 1	command to input the contents of document 1 as standard
Identifier qualified input	Commands << identifiers	Command reads content from standard input until it encounters the identifier delimiter position
Input and output redirection	Command < file 1 > file 2	command to use the contents of document 1 as standard input, file 2 as standard output

(Content of reference: http://blog.csdn.net/cjfeii/article/details/10084343)