Common commands for the Linux Foundation

Common commands:

Linux File system:

1, the file name strictly distinguishes the character casing;

2, the file can use any character except/;

3, the file name can not exceed 255 characters;

4. The file that starts with. is a hidden file;

.: Current directory;

.: The top level directory of the current directory;

/etc/sysconfig/

.: Sysconfig

..:/etc

Working directory: Working directory

Home directory: Home

Common commands:

Pwd:printing working Directory

Show working directory

Cd:change Directory

CD [/path/to/somedir]

CD: Switch home directory;

Note: in bash, ~ denotes home directory;

CD ~: Switch back to your home directory

CD ~username: Switch to the home directory of the specified user;

CD-: Switch back and forth between the last directory and the current directory;

Related environment variables

$PWD: Current Working directory

$OLDPWD: Last working directory

Ls:list, listing the contents of the specified directory

ls [OPTION] ... [FILE] ...

-A: Displays all files, including hidden files;

-A: Displays except. and. All documents other than the

-L:--long, long format list, which displays detailed attribute information of the file;

-rw-r--r--. 1 root root 8957 October 19:34 boot.log

-: File type,-, D, B, C, L, S, p

rw-r--r--

rw-: The permission of the owner of the file;

r--: Permissions of the file group;

r--: Other users (not the owner, belong to the group) of the Authority;

1: Number indicates the number of times the file has been hard-linked;

Root: The owner of the file;

Root: The genus of the file;

8957: number indicates the size of the file, in bytes;

October 14 19:34: The time the file was last modified;

Boot.log: File name

-H,--human-readable: The file size unit conversion, after the conversion results may be non-accurate values;

-D: View the directory itself rather than its internal file list;

-r:reverse, reverse display;

-r:recursive, recursive display;

Cat:concatenate

file text Viewing tool;

Cat/etc/fstab

cat/etc/passwd

Cat [OPTION] ... [FILE] ...

-N: The number of text lines to display;

-E: Displays the line terminator $;

Tac

file text Viewing tool;

Tac/etc/fstab

tac/etc/passwd

TAC [OPTION] ... [FILE] ...

-N: The number of text lines to display;

-E: Displays the line terminator $;

File: View the document content type;

file [file] ...

Echo: Echoing

echo [Short-option] ... [STRING] ...

-N: No line break;

-E: Let the escape character take effect;

\ n: Line break

\ t: Tab

String can use quotation marks, single and double quotation marks are available;

Single quotes: Strong references, variable references do not perform substitutions;

~]# Echo ' $SHELL '

Double quotes: Weak references, variable references are replaced;

~]# echo "$SHELL"

Note: Regular symbols for variable references

${name}

Shutdown or restart command: shutdown

Shutdown [OPTIONS ...] [TIME] [WALL ...]

OPTIONS:

-h:halt

-r:reboot

-c:cancel

Time:

Now

hh:mm

+m

+0

WALL

Date-related commands:

Linux: The date and time information is read from the hardware when the system starts, and after the reading is completed, it is no longer associated with the hardware;

System clock

Hardware clock

Date: System clock

Display Date Time: Date [OPTION] ... [+format]

Format: Formatting characters

%F

%T

%Y

%m

%d

%H

%M

%s

%s: from January 1, 1970 (Unix) 0 points 0 minutes 0 seconds to the command execution that moment elapsed the number of seconds;

...

Set Date time: Date [MMDDHHMM[[CC]YY][.SS]]

Hwclock, clock: Hardware clocks

Display or set the hardware clock

-S,--hctosys: Hardware-based, the system is adjusted to the same time as the hardware;

-W,--SYSTOHC: The hardware time is adjusted to be the same as the system clock, whichever is the system;

Cal: Calendar

Cal [[month] year]

Common commands for the Linux Foundation