Linux / dev/null block devices: empty Devic

/ dev/null belongs to a special character file, it is an empty device, it is a special device file, it will discard all the data written into it, the content written to it will be lost forever, and there is nothing to read.

Let's use the file command to check that the type is a character special file.

Sume@gec:~$ file / dev/null/dev/null: character special

Attempt to read with the cat command

Sume@gec:~$ cat / dev/sdacat: / dev/sda: Permission deniedsume@gec:~$ cat / dev/nullsume@gec:~$

I can't read anything.

In applications, messages that do not need to be printed in the window are generally thrown into / dev/null, such as error messages.

Sume@gec:/mnt/hgfs/1725/speak_class/mulcast$ cat ls.txtcat: ls.txt: No such file or directorysume@gec:/mnt/hgfs/1725/speak_class/mulcast$ cat ls.txt 2 > / dev/null # (2 is a standard error) redirects the error message of ls.txt to / dev/null, so the error message does not print sume@gec:/mnt/hgfs/1725/speak_class/mulcast$