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This article will explain in detail what are the user management and file system commands in Linux. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Basic command

Commands for Linux systems are usually in the following format:

Command name [named parameter] [command object]

Get login information

Get login information-"w" / "who" / "last" / "lastb".

Maoli@ubuntu:~$ w 08:07:38 up 2 min, 1 user, load average: 0.83, 0.64 0.27 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT maoli tty7: 0 08:06 2:38 2.29s 0.31s / sbin/upstart-maoli@ubuntu:~$ who maoli tty7 2020-05-28 08:06 (: 0) maoli@ubuntu:~$ last maoli tty7: 0 Thu May 28 08:06 gone-no logout reboot system boot 4.15.0-99-generi Thu May 28 08:04 still running maoli tty7: 0 Fri May 1 15:20-down (01:26) reboot system boot 4.15.0-99-generi Fri May 1 15:20-16:47 (01:26) maoli tty7: 0 Fri May 1 10:12-crash (05Fri May 08) wtmp begins Fri May 1 10:12:22 2020 maoli@ Password for ubuntu:~$ sudo lastb [sudo] maoli: btmp begins Fri May 1 15:20:29 2020

Check the Shell you use

Check out the Shell-"ps" you use.

Shell, also known as "shell" or "shell program", is the translator of the communication between the user and the operating system kernel, which is simply the interface and interface between human and computer. At present, the default Shell of many Linux systems is bash (Bourne Again SHell), because it can use the tab key for command and path completion, save history commands, easily configure environment variables, and perform batch operations.

Maoli@ubuntu:~$ ps PID TTY TIME CMD 3621 pts/1 00:00:00 bash 5082 pts/1 00:00:00 ps

View the description and location of the command

View the description and location of the command-"whatis" / "which" / "whereis".

Maoli@ubuntu:~$ whatis ps ps (1)-report a snapshot of the current processes. Maoli@ubuntu:~$ whatis python python (1)-an interpreted, interactive, object-oriented programmi... Maoli@ubuntu:~$ whereis ps ps: / bin/ps / usr/share/man/man1/ps.1.gz maoli@ubuntu:~$ whereis python python: / usr/bin/python3.5m-config / usr/bin/python / usr/bin/python3.5 / usr/bin/python3.5m / usr/bin/python2.7 / usr/bin/python3.5-config / usr/lib/python3.5 / usr/lib/python2.7 / etc/python / etc/python3.5 / etc/python2.7 / usr/local/lib/python3.5 / usr/local/lib/python2.7 / usr/include/python3.5 / usr/include/python3.5m / usr/share/python / usr/share/man/man1/python.1.gz maoli@ubuntu:~$ which ps / bin/ps maoli@ubuntu:~$ which python / usr/bin/python

Clear what is displayed on the screen

Clear what appears on the screen-"clear".

Check the help documentation-"man" / "info" / "help" / "apropos".

Maoli@ubuntu:~$ ps-- help Usage: ps [options] Try'ps-- help'or'ps-- help 'for additional help text. For more details see ps (1). Maoli@ubuntu:~$ man ps PS (1) User Commands PS (1) NAME ps-report a snapshot of the current processes. SYNOPSIS ps [options] DESCRIPTION...

View system and hostname

View the system and hostname-"uname" / "hostname".

Maoli@ubuntu:~$ uname Linux maoli@ubuntu:~$ hostname ubuntu

Time and date

Time and date-"date" / "cal".

Maoli@ubuntu:~$ date May 28, 2020 Thursday 08:13:25 CST maoli@ubuntu:~$ cal May 2020 1, 2, 3, 4, 5, 5, 6, 6, 6, 6, 9, 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 26 27 28 29 30 31 maoli@ubuntu:~$ cal 5 2020 May 2020 one, two, three, four, five, six, 12, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 25, 26, 27, 29, 30 31

Restart and shut down

Restart and shutdown-"reboot" / "shutdown"

Maoli@ubuntu:~$ shutdown-h + 5 # five-minute shutdown Shutdown scheduled for four 2020-05-28 08:19:24 CST, use 'shutdown-c' to cancel. [root] # maoli@ubuntu:~$ shutdown-c maoli@ubuntu:~$ shutdown-r 12:00 Shutdown scheduled for four 2020-05-28 12:00:00 CST, use 'shutdown-c' to cancel maoli@ubuntu:~$ shutdown-c

Note: when executing the shutdown command, a warning will be issued to the user who logs in to the system. You can replace the default warning message by following the warning message, or you can use now to shut down immediately after the-h parameter.

Log out

Log out-"exit" / "logout".

View history command

View the history command-"history".

Maoli@ubuntu:~$ history... 625 date 626 cal 627 cal 5 2020 628 shutdown-c 629 shutdown-r 12:00 630 shutdown-c 631 history maoli@ubuntu:~$! 631

Description: after viewing the history command, you can use it! The historical command number is re-executed; the historical command can be cleared through history-c.

Utility program

File and folder operations

Create / delete empty directory

Create / delete empty directory-"mkdir" / "rmdir".

[root ~] # mkdir runsen [root ~] # mkdir-p abc/runsen [root ~] # rmdir runsen

Create / delete files

Create / delete files-"touch" / "rm".

Maoli@ubuntu:~$ touch readme.txt maoli@ubuntu:~$ rm readme.txt rm: remove regular empty file 'readme.txt'? Y [root ~] # rm-rf; xyz 

The touch command is used to create a blank file or modify the file time. In a Linux system, there are three times for a file:

When the content was changed-mtime.

When the permission was changed-ctime.

Last visit time-atime.

Several important parameters of rm:

-I: interactive deletion, each deleted item will be asked.

-r: delete the directory and recursively delete the files and directories in the directory.

-f: force deletion, ignore files that do not exist, without any prompts.

Toggle and view the current working directory

Switch and view the current working directory-"cd" / "pwd".

Description: the cd command can be followed by a relative path (with the current path as a reference) or an absolute path (starting with /) to switch to the specified directory, or you can use cd.. To return to the previous directory. Returning to the directory above should be given to cd.. /. / command.

View the contents of the directory

Check the contents of the directory-"ls".

-l: view files and directories in a long format.

-a: displays files and directories that begin with a dot (hidden files).

-R: recursively expand when you encounter a directory (continue to list the files and directories under the directory).

-d: only directories are listed, nothing else is listed.

-S /-t: sort by size / time.

View the contents of the file

View the contents of the file-"cat" / "tac" / "head" / "tail" / "more" / "less" / "rev" / "od".

Maoli@ubuntu:~$ wget https://www.csdn.net/-- 2020-05-28 08 www.csdn.net-- https://www.csdn.net/ is parsing host www.csdn.net (www.csdn.net). 47.95.164.112 www.csdn.net (www.csdn.net) is being connected | 47.95.164.112 |: 443. Connected. HTTP request issued, waiting for response. 200 OK length: unspecified [text/html] saving to: "index.html" index.html [] 420.39K 1.53MB/s in 0.3s 2020-05-28 08:25:02 (1.53MB/s)-"index.html" saved [430482] maoli@ubuntu:~$ cat index.html.. Maoli@ubuntu:~$ head-10 index.html CSDN- Professional IT Technology Community maoli@ubuntu:~$ tail-2 index.html maoli@ubuntu:~$ less index.html # is equivalent to cat maoli@ubuntu:~$ cat-n index.html | more.

Description: the above uses a command called wget, which is a network downloader program that can download resources from the specified URL.

Copy / move files

Copy / move files-"cp" / "mv".

Maoli@ubuntu:~$ mkdir backup maoli@ubuntu:~$ cp index.html backup/ maoli@ubuntu:~$ cd backup/ maoli@ubuntu:~/backup$ ls index.html maoli@ubuntu:~/backup$ mv index.html csdn.html maoli@ubuntu:~/backup$ ls csdn.html

File renaming

File rename-"rename".

Find files and find content

Find files and find content-"find" / "grep".

Maoli@ubuntu:~/backup$ find. /-name "* .html". / csdn.html maoli@ubuntu:~/backup$ find /-name "* .html" / usr/local/java/jdk-11.0.6/README.html / usr/local/python3/lib/python3.6/idlelib/help.html / usr/local/python3/lib/python3.6/test/sgml_input.html / usr/local/python3/lib/python3.6/test/test_difflib_expect.html. Maoli@ubuntu:~/backup$ find. -type f-size + 2k. / csdn.html maoli@ubuntu:~/backup$ find. -type f-name "* .swp"-delete maoli@ubuntu:~/backup$ grep "csdn.html-n 3192: maoli@ubuntu:~/backup$ grep-E\ csdn.html-n 12: 18: 19:...

Description: grep can use regular expressions when searching for strings. If you need to use regular expressions, you can use grep-E or directly use egrep.

Create and view links

Create links and view links-"ln" / "readlink".

Maoli@ubuntu:~/backup$ ls-l csdn.html-rw-rw-r-- 1 maoli maoli 430482 May 28 08:30 csdn.html maoli@ubuntu:~/backup$ ln / home/maoli/backup/csdn.html / home/maoli/csdn maoli@ubuntu:~/backup$ ls-l csdn.html-rw-rw-r-- 2 maoli maoli 430482 May 28 08:30 csdn.html

Description: links can be divided into hard links and soft links (symbolic links). Hard links can be thought of as a pointer to file data, just like the reference count of objects in Python. Each time a hard link is added, the number of corresponding links in the file increases by 1. Only when the number of links in the file is 0, the storage space corresponding to the file can be overwritten by other files. In fact, when we delete files, we do not delete the data on the hard disk, we delete only a pointer, or a record of the use of data, so software such as "file shredder" will not only delete the file pointer when "shredding" the file, but also fill in the corresponding storage area of the file with data to ensure that the file cannot be recovered. Soft links are similar to shortcuts in Windows systems. When the files linked by the soft link are deleted, the soft link becomes invalid.

Compress / decompress and archive / unarchive

. Compress / decompress and archive / unarchive-"gzip" / "gunzip" / "xz".

Maoli@ubuntu:~$ ls redis-4.0.10.tar.tar.gz maoli@ubuntu:~$ gunzip redis-4.0.10.tar.tar.gz maoli@ubuntu:~$ ls redis-4.0.10.tar.tar

Filing, settlement and archiving

Filing and settlement filing-"tar".

Maoli@ubuntu:~$ tar-xvf redis-4.0.10.tar redis-4.0.10/ redis-4.0.10/.gitignore redis-4.0.10/00-RELEASENOTES redis-4.0.10/BUGS redis-4.0.10/CONTRIBUTING redis-4.0.10/COPYING redis-4.0.10/INSTALL redis-4.0.10/MANIFESTO redis-4.0.10/Makefile redis-4.0.10/README.md redis-4.0.10/deps / redis-4.0.10/deps/Makefile redis-4.0.10/deps/README.md...

Note: tar command is used for archiving (also known as creating archive) and archiving. Usually, three parameters are required to create an archive, where c means to create (create), v means to display the details of creating an archive (verbose), and f represents a file to be specified (file). De-archiving requires the parameter-xvf, where x means extract, and the other two parameters are the same as creating an archive.

Convert standard input to command line arguments

Convert the standard input to the command line argument-"xargs".

The following command will find the html files under the current path, and then pass these files as parameters to the rm command through xargs to find and delete files.

Maoli@ubuntu:~$ find. -type f-name "* .html" | xargs rm-f

The following command turns the multi-line contents of the a.txt file into one line of output to the b.txt file, which means that the result of the execution of the command is output to b.txt.

Maoli@ubuntu:~$ xargs

< a.txt >

B.txt

Show files or directories

Display the file or directory-"basename" / "dirname".

Other related tools

Other related tools.

"sort"-sorts content

"uniq"-remove adjacent duplicates

"tr"-replace the specified content with the new content

"cut" / "paste"-cut / paste content

"split"-split Fil

"file"-determines the file type

"wc"-counts the number of file lines, words, and bytes

"iconv"-Transcoding

Maoli@ubuntu:~$ cat foo.txt grape apple pitaya maoli@ubuntu:~$ cat bar.txt 100200 300400 maoli@ubuntu:~$ paste foo.txt bar.txt grape 100 apple 200 pitaya 300400 maoli@ubuntu:~$ paste foo.txt bar.txt > hello.txt maoli@ubuntu:~$ cut-b 4-8 hello.txt pe 10 le 20 aya 30 maoli@ubuntu:~$ cat hello.txt | tr'\ t', 'grape,100 apple,200 pitaya,300 400 maoli@ubuntu:~$ split-l 100 sohu.html hello maoli@ubuntu:~$ wget https://www.baidu.com/img/bd_logo1.png maoli@ubuntu:~$ file bd_logo1.png bd_logo1.png: PNG image data, 540 x 258, 8-bit colormap, non-interlaced maoli@ubuntu:~$ wc index.html 3820 18696 430482 index.html maoli@ubuntu wget http://www.qq.com-O qq.html maoli@ubuntu iconv-f gb2312-t utf-8 qq.html

Use of pipes and redirected pipes

Use of pipes-"|".

Example: find the number of files in the current directory.

Maoli@ubuntu:~$ find. / | wc-l 80801

Example: list the files and folders under the current path and add a number to each item.

Maoli@ubuntu:~$ ls | cat-n 1 abc 2 backup

Example: find the total number of records in the record.log that contain AAA but not BBB

Maoli@ubuntu:~$ cat record.log | grep AAA | grep-v BBB | wc-l

Output redirection

Output redirection and error redirection-">" / ">" / "2 >".

Maoli@ubuntu:~$ cat readme.txt banana apple grape apple grape watermelon pear pitaya maoli@ubuntu:~$ cat readme.txt | sort | uniq > result.txt maoli@ubuntu:~$ cat result.txt apple banana grape pear pitaya watermelon

Input redirection

Enter redirect-"hello.txt maoli@ubuntu:~$ echo'I will show you some code.' > > hello.txt maoli@ubuntu:~$ cat hello.txt hello, world! I will show you some code.

Multiple orientation

Multiple orientations-"tee".

In addition to displaying the results of the command ls on the terminal, the following command is appended to the ls.txt file.

Maoli@ubuntu:~$ ls | tee-a ls.txt maoli@ubuntu:~$ cat ls.txt abc backup

Alias

"alias" creates an alias

Maoli@ubuntu:~$ alias ll='ls-1 'maoli@ubuntu:~$ alias frm='rm-rf' maoli@ubuntu:~$ ll quantity 144920 drwxrwxr-x 3 maoli maoli 4096 May 28 08:20 abc maoli@ubuntu:~$frm abc

"unalias" removes aliases

Maoli@ubuntu:~$ funalias frm maoli@ubuntu:~$ frm index.html-bash: frm: command not found

Text processing character stream editor

Character stream editor-"sed".

Sed is a tool for manipulating, filtering, and transforming text content. Suppose you have a file called fruit.txt, which looks like this.

Maoli@ubuntu:~$ cat-n fruit.txt 1 banana 2 grape 3 apple 4 watermelon 5 orange

Next, we add a pitaya after line 2.

Maoli@ubuntu:~$ sed'2a pitaya' fruit.txt banana grape pitaya apple watermelon orange

Insert a waxberry before line 2.

Maoli@ubuntu:~$ sed'2i waxberry' fruit.txt banana waxberry grape apple watermelon orange

Delete line 3.

Maoli@ubuntu:~$ sed '3d' fruit.txt banana grape watermelon orange

Delete lines 2 through 4.

Maoli@ubuntu:~$ sed '2pr 4d' fruit.txt banana orange

Replace the character an in the text with @.

Maoli@ubuntu:~$ sed's favorite fruit.txt b@nana gr@pe @ pple w@termelon or@nge

Replace the character an in the text with @ and use global mode.

Maoli@ubuntu:~$ sed 'fruit.txt bounded natively @ gr@pe @ pple w@termelon or@nge

Pattern matching and processing language

Pattern matching and processing language-awk.

One of the authors and current maintainers of awk, a programming language and the most powerful tool for handling text in Linux systems, is the previously mentioned Brian Kernighan (the closest partner of ken and dmr). Through this command, we can extract the specified columns from the text, extract what we want from the text with regular expressions, display the specified lines, and perform statistics and operations. In short, it is very powerful.

Suppose you have a file called fruit2.txt, which looks like this.

\ maoli@ubuntu:~$ cat fruit2.txt 1 banana 120 2 grape 500 3 apple 1230 4 watermelon 80 5 orange 400

Line 3 of the file is displayed.

Maoli@ubuntu:~$ awk 'NR==3' fruit2.txt 3 apple 1230

Displays the second column of the file.

Maoli@ubuntu:~$awk'{print $2} 'fruit2.txt banana grape apple watermelon orange

Displays the last column of the file.

Maoli@ubuntu:~$ awk'{print $NF} 'fruit2.txt 120500 1230 80400

Output lines with numbers greater than or equal to 300 at the end.

Maoli@ubuntu:~$ awk'{if ($3 > = 300) {print $0}} 'fruit2.txt 2 grape 500 3 apple 1230 5 orange 400

User management

Create and delete users

Create and delete users-"useradd" / "userdel". Need to use root account to create

Maoli@ubuntu:~$ su root password: root@ubuntu:/home/maoli# useradd Runsen root@ubuntu:/home/maoli# userdel Runsen

-d-specify the user home directory for the user when creating the user

-g-specify the user group to which the user belongs when creating the user

Create and delete user groups

Create and delete user groups-"groupadd" / "groupdel".

The main purpose of a user group is to facilitate the management of all users in a group.

Modify the password

Change password-"passwd".

Root@ubuntu:/home/maoli# passwd maoli New password: Retype new password: passwd: all authentication tokens updated successfully.

If you do not specify an object for which the command acts when using the passwd command, you want to change the password of the current user. If you want to change the user's password in bulk, you can use the chpasswd command.

-l /-u-locks / unlocks the user.

-d-clears the user password.

-e-sets the password to expire immediately and will be forced to change the password when the user logs in.

-I-sets the number of days after the password expires to disable the user.

View and modify password validity View and modify password validity-"chage".

The password must be changed after setting the maoli user for 100 days, notify the user 15 days before expiration, and disable the user 15 days after expiration.

Root@ubuntu:/home/maoli# chage-M100-W 15-I 15 maoli

Switch users-"su".

Root@ubuntu:/home/maoli# su maoli maoli@ubuntu:~$

Execute commands as an administrator

Execute the command-"sudo" as an administrator.

Maoli@ubuntu:~$ ls / root ls: cannot open directory / root: Permission denied maoli@ubuntu:~$ sudo ls / root [sudo] password for maoli:

"description": if you want the user to be able to execute the command as an administrator, the user must appear in the sudoers list. The sudoers file is in the / etc directory. If you want to edit the file directly, you can also use the following command.

Edit the sudoers file

Edit sudoers file-"visudo".

The editor used here is vim, and the knowledge about vim is explained earlier.

52. Some of the contents of this file for ViM are as follows:

# # Allow root to run any commands anywhere root ALL= (ALL) ALL # # Allows members of the 'sys' group to run networking, software, # # service management apps and more. #% sys ALL= NETWORKING, SOFTWARE, SERVICES, STORAGE, DELEGATING, PROCESSES, LOCATE, DRIVERS # # Allows people in group wheel to run all commands% wheel ALL= (ALL) ALL # # Same thing without a password #% wheel ALL= (ALL) NOPASSWD: ALL # # Allows members of the users group to mount and unmount the # cdrom as root #% users ALL=/sbin/mount / mnt/cdrom, / sbin/umount / mnt/cdrom # # Allows members of the users group to shutdown this system #% users localhost=/sbin/shutdown-h now

Display information for users and user groups

Displays information about users and user groups-"id".

Root@ubuntu:/home/maoli# id uid=0 (root) gid=0 (root) group = 0 (root)

Send messages to other users

Send messages to other users-"write" / "wall".

Sender:

Root@ubuntu# write maoli Hello Maoli EOF

Type EOF to indicate the end of the message and use the Crtl+D key combination to send the message. The input appears on the user's screen and the communication is aborted. Recipient:

Maoli@ubuntu:~$ Message from root on pts/0 at 9:41... Hello Maoli EOF

Check / set whether to receive messages from other users-"mesg".

Maoli@ubuntu:~$ mesg is y maoli@ubuntu:~$ mesg n maoli@ubuntu:~$ mesg is n

If you want to send a message to all users in the system, you can use the wall command, wall says: write all. Enter wall, and then edit the information. If shell supports it, you can use Chinese. Then use the Crtl+D key combination to send the message. In this way, the desktops of all logged-in users of the system will receive a message. If you are on a network, you can use the rwall command to send information to all users on the local area network.

File system

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File and path naming rules: the maximum length of a file name is related to the file system type. in general, a file name should not exceed 255 characters, although most characters can be used for file names. however, it is best to use symbols such as uppercase and lowercase letters, numbers, underscores and dots. Although spaces can be used in file names, spaces should be avoided as much as possible, otherwise when entering a file name, you need to enclose the file name in double quotes or escape spaces by\.

Extension: the extension of a file is optional on the Linux system, but using an extension helps to understand the contents of the file. Some applications identify files by extension, but more applications do not rely on file extensions, just as the file command does not determine the type of file by its extension.

Hidden files: files that begin with a dot are hidden files (invisible files) on Linux systems.

Directory structure

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/ bin-binary file for basic commands.

/ boot-Boot loader's static file.

/ dev-device file.

"/ etc"-profile.

/ home-the parent directory of the normal user's home directory.

/ lib-shared library files.

/ lib64-share 64-bit library files.

/ lost+found-stores unlinked files.

/ media-automatically identifies the mount directory of the device.

/ mnt-the mount point where the file system is mounted temporarily.

/ opt-optional plug-in package installation location.

/ proc-Kernel and process information.

"/ root"-Super Admin user home directory.

/ run-stores what is needed when the system is running.

/ sbin-binary file for the superuser.

/ sys-pseudo file system of the device.

/ tmp-temporary folder.

"/ usr"-user application directory.

/ var-variable data directory.

Access permission

Change the file mode

1. "chmod"-changes the file mode bit.

Total amount of maoli@ubuntu:~/backup$ ls-l 424-rw-rw-r-- 2 maoli maoli 430482 May 28 08:30 csdn.html maoli@ubuntu:~/backup$ chmod Grouw Total csdn.html maoli@ubuntu:~/backup$ ls-l 424-rw-rw-rw- 2 maoli maoli 430482 May 28 08:30 csdn.html maoli@ubuntu:~/backup$ chmod 644 csdn.html maoli@ubuntu:~/backup$ ls-l total consumption 424-rw-r--r-- 2 maoli maoli 430482 May 28 08:30 csdn.html

Description: through the above example, we can see that there are two ways to change the file mode bits with chmod: one is character setting method, the other is digital setting method. In addition to chmod, you can use umask to set which permissions will be removed from the default permissions of the new file.

Change the owner of the file

2. "chown"-change the file owner.

Total amount of maoli@ubuntu:~/backup$ ls-l 424-rw-r--r-- 2 maoli maoli 430482 May 28 08:30 csdn.html maoli@ubuntu:~/backup$ sudo chown root csdn.html [sudo] maoli password: maoli@ubuntu:~/backup$ ls-l total dosage 424-rw-r--r-- 2 root maoli 430482 May 28 08:30 csdn.html

3. "chgrp"-change the user group.

This is the end of this article on "what are the user management and file system commands in Linux?". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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