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This article mainly introduces what are the redirect commands under Linux, which can be used for reference by interested friends. I hope you can learn a lot after reading this article.

Linux redirection refers to modifying some of the original default things, changing the default execution mode of the original system commands, for example, simply I do not want to see the output in the monitor but want to output to a file, I can do this work through Linux redirection.

1. Redirect: 1. Output redirection: causes the user to redirect the output of a command to a file instead of displaying it on the screen: 1 >: overwrite 1 > >: append 2. Error redirection: 2 > 2 > > 13. Both right and wrong are redirected to the same location: 2 > & 1; & >

two。 Command wildcard: * matches any character of any length? Match any single character [] match any single character within the specified range [^] match any single character outside the specified range [[: upper:] all uppercase letters [: lower:]] all lowercase letters [[: alpha:]] match all letters [: digit:]] all numbers [: alnum:] letters and numbers [: space:]] white space characters [[: Punct:]] punctuation marks show details

3. Common command: 1.ls command usage: ls:ls [OPTION]. [FILE]...

Option usage ls lists files and directories under the current directory-a shows all files including hidden files-A shows all files including hidden files but except. And... -c is sorted by ctime,-lt is used together with-l to display information such as file attributes and permissions in long data format-t is sorted by modification time-d lists the directory itself, instead of the contents of the directory-I list the inode number of the file is generally used with-l to display the file size in kB MB GB format 2.pwd command usage: pwd: show the current working directory absolute path-L: display the current path Whether there is a linked file or not, it is displayed with no options-P: displays the current path, and if there is a linked file, directly displays the file to which the linked file points

3.cd command usage: cd: change the working directory ~: user's home directory -: represents the previous working directory. Superior directory.: current directory

4.date command usage: date: display or modify the system time and date date [OPTION]. [+ FORMAT] date [- u |-utc |-universal] MMDDhhmm [[CC] YY]

-d "string": the date and time referred to in the string do not represent the current time not now-s "string": set the date and time according to the string 5.passwd command usage: passwd: set the user password (only root users have permission to use it)

Option usage-password can still be used after k expires-llock, lock user password, only root has permission to operate-u unlock-f mandatory operation: only root has permission-n days: minimum number of days for two password changes-x days days for two password changes-stdin password to obtain password from standard input Non-interactive setting password use-w days distance how many days to remind the user to change the password-S query password status-how many days after the I days password expires, the user is disabled to display details

6.su command usage: su: change the user identity su-username-c commond: change the user to the user of user, execute the commomd command, and then change back to the original user -: the user's environment variable switch

7. Clear screen: clear= CTRL+L

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