One, system commands
1. Poweroff: Shut down directly
2，shutdown：
-h: Shut down the system;
-k: Only send information to all users, but will not actually shut down;
-r: restart after shutdown;
-t<number of seconds>: How many seconds to delay between sending the warning message and deleting the message.
3. reboot: restart
4. Halt: shutdown (only for system administrators)
5. Who: Display all users of the system
6, whoami: display the current user
7, w: Display current user information
Two, system settings
1, clear: clear the screen
Three, system management
1, su: switch to other users
2. Date: display or set the date and time of the system
3. Cal: the current calendar, or the calendar of the specified date
4. alias: set the alias of the instruction
5. unalias: cancel the command alias
Fourth, disk management
1, pwd: display the current working directory
2, ls: display the contents of the specified working directory
3. cd: switch the current working directory
"~" also means home directory
"." means the current directory,
".." means the directory one level above the current directory location
4. mkdir: create a directory
-p Create directories recursively
5. rmdir: delete directory
-p Create directories recursively
5. du: used to display the size of a directory or file
-m or --megabytes in units of 1MB.
-s or --summarize only displays the total
-k or --kilobytes in units of 1024 bytes
-b or -bytes When displaying the directory or file size, the unit is byte
6.dd: backup files
if=file name: input file name, default is standard input. Specify the source file
of=file name: output file name, default is standard output. Designated destination file
7, stat: display detailed file information
Five, help instructions
1. man: View information such as external command help, configuration file help and programming help in Linux
2, help: View the help information of internal commands
3. Whatis: query what function a command performs, and print the query result to the terminal
Six, file management
1, whereis: command is used to find files
-b Only find binary files.
-B only find binary files in the set directory
-f does not display the path name before the file name
-m only find documentation
-M Only find the description file in the set directory
-s only find the original code file
-S only find the original code file in the set directory
-u Find files that do not contain the specified type
2. cp: copy files or directories
3. mv: Rename the file or directory, or move the file or directory to another location
4. touch: create a file
5. rm: delete files
-f Even if the original file attribute is set to read only, it will be deleted directly without confirming one by one
6. cat/tac: display the content of the file/display the content of the file in reverse order
-n Numbers all output lines starting with 1;
-b is similar to -n, except that blank lines are not numbered;
-s When encountering more than two consecutive blank lines, replace them with a single blank line
7, more/less: paging display content
8, head/tail: intercept the content of the document from the head/tail
-c number of bytes displayed
-n displays the last n lines of the file
9, cut: intercept column content
-d: custom separator
-f: Used with -d to specify which column to display
10, locate: find documents that meet the conditions
-b matches the file under the path name
-c only output the number found
11. Find: Find files in the specified directory
12. file: file command is used to identify file types
-b When listing recognition results, do not display the file name
13, ln: file creation connection
-b Delete, overwrite the backup before the target file
-d Establish a hard link to the directory
-f Force a file or directory link, regardless of whether the file or directory exists
-i Ask the user before overwriting an existing file
-n The purpose of the symbolic link The directory is treated as a normal file
-s to establish a symbolic link to the source file, not a hard link
Seven, document editing
1, sort: for the content of the text file, sort by line
-b Ignore the space characters at the beginning of each line
-c Check whether the file has been sorted in order
-d When sorting, deal with English letters, numbers and space characters, and ignore other characters
-f When sorting, treat lowercase letters as uppercase letters
-m merge several sorted files
-M Sort the first 3 letters according to the abbreviation of the month
-n sort by value
-u means unique (unique), and the output result is completely heavy
-r sort in reverse order
2. uniq: command is used to check and delete repeated rows and columns in text files
-c displays the number of recurrences of the row next to each column
-d displays only recurring ranks
-f ignores the specified field for comparison
-u displays the ranks only once
3. wc: Calculate the number of bytes, words, or columns of the file
-c only displays the number of Bytes
-l only display the number of lines
-w only display the number of words
4. grep: find the qualified string in the file
-c Calculate the number of columns that meet the template style
-n before displaying the column that conforms to the template style, mark the number of the column
Eight, special characters
1, "^" line beginning
2. "%" at the end
3. "|" pipe character