Linux Shell redirection

Linux file descriptor: Three file descriptors are opened by default: standard input 0, standard output 1, error output 2

Output redirection

Command-line1 [1-N]> file or file operator or device

First, check whether the file on the right exists. If the file exists, delete it and create it again. No matter whether the command on the left is executed successfully or not, the file on the right will become empty. Use> to append the object.

[UNIX @17:18:57 ~] $ Ls>A.txt
[UNIX @17:19:11 ~] $ Cat a.txt
A.txt
CPP
Ctest
Makefile
Network
Shell
Socket
Test
Thread
 

Input redirection

Command-line [N] <file or file descriptor & Device

[Unix@17:20:59~]$ Cat>A <a.txt
[Unix@17:21:36~]$ CatA
A.txt
CPP
Ctest
Makefile
Network
Shell
Socket
Test
Thread
 

Exec binding redirection

Exec file descriptor [N] <or> file or file descriptor or device

As mentioned above, the output redirection will bind the input. After the output is bound to a file or device, it is only valid for the current command. If you need to bind all the subsequent commands to be supported, you need to use the EXEC command.

 [Unix  @  17  :  26  :  02  ~]  $ Exec     1  >  A.txt
[Unix  @  17  : 26  :  11  ~]  $ Ls     -  Al
[Unix  @  17  :  26  :  16  ~]  $ Exec     1 >/  Dev  /  Tty  #  Restore standard output  
  [Unix  @  17  :  26  :  25  ~]  $ Ls  
A.txt CPP ctest makefile network shell socket test thread