Linux Common Command points

①cd:change Directory

CD: The home directory is returned by default without any parameters.

CD ~username: Enter the home directory of the specified user

CD-: Switch back and forth between the current directory and the previous directory

Ii

<> must choose

[] Optional

... can appear multiple times

| Choose one More

{} grouping

③

Mans:

Name: command names and features brief description

Synopsis: Usage notes, including available options

DESCRIPTION: A detailed description of the command function, which may include the meaning of each option

options: Explaining the meaning of each option

Files: The configuration file associated with this command

BUGS:

EXAMPLES: Using the example

See also: another reference

Flip Screen

Turn back one screen: SPACE

Turn One screen forward: b

Turn down one line: ENTER

Turn One line forward: K

Find

/keyword backwards

N: Next

N: Previous

　　

? KEYWORD forward

N: Next

N: Previous

Q: Exit

④

mkdir: Create empty Directory The last one is the directory node created

-P

-v:verbose

mkdir-pv/x/m/x/n

= MKDIR-PV/{x/m,n}

Command line expansion

Tips:

A_b,a_c,d_b,d_c

={A,D}_{B,C}

⑤

Directory Management:

ls cd madir rmdir tree pwd

File Management:

Touch Stat file RM CP MV

Date Time

Date Clock Hwclock cal

To view text:

Cat, TAC, more, less, head, tail

Text Processing:

Cut, join SED, awk, grep, sort

⑥

Command line editing

Cursor Jump:

CTRL + A: Skip to the beginning of the command

Ctrl+e: Jump to the end of the command line

Ctrl+u: Delete the cursor to the beginning of the command line

CTRL+K: Delete the cursor to the end of the command line

Ctrl+l: Clear Screen

Ctrl+d: Delete the character of the cursor

⑦

Command history

View command history: Historical

-C: Command to empty command history

-D offset[n]: Delete command at specified location

-D 500 10 Delete 10 from No. 500

-A: Writes the command in the history command buffer to the history command file;

-r: Reads commands from the history command file into the current History command buffer;

-W: Writes the current History command buffer command to the history command file.

Environment variables

Path: Command Search Path

Histsize: Command history buffer size

echo $HISTSIZE Default is 1000

Command history Usage Tips:

！ N: Executes the nth command in the command history:

！ -N: Executes the last nth command in the command history:

！！ : Executes the previous command

！ String: The most recent command in the command history that starts with the specified string

！ $: Reference the last parameter of the previous command;

Esc.

ALT +.: Support only in the terminal

⑧

command completion, command aliases, command substitution

Command completion:

Each path specified by the search PATH environment variable is next to the one we give

The string at the beginning of the executable file, if more than, two times tab,

The list can be given, otherwise it will be directly complete.

Path Completion:

Search for each file name under the starting path we gave, and try to complete the completion.

Command aliases:

Alias cmdalias= ' COMMAND [options] [arguments] '

Aliases defined in the shell are valid only in the current Shell life cycle;

The valid range of aliases is the current shell process;

To be effective, you need to modify the configuration file.

Ualias Comalias

\cmd: Using the command itself

Command substitution:

$ (COMMAND []: []..) = = Anti-quote: ' COMMAND '

The process of replacing a command with a self-command in its execution result

Touch./file-$ (date +%f-%h-%m-%s). txt

Quotes supported by bash:

·· : Command substitution

"": weak reference, you can implement variable substitution:

': Strong reference, do not complete variable substitution

⑨

File name wildcard

Globbing

*: Any character of any length

？ : Any single character

[]: matches any single character within the specified range

[Abc],[a-m],[a-z],[a-za-z]

[: Space:]: Blank

[:p UNCT:]: Punctuation

[: Lower:]: lowercase letters

[: Upper:]: Uppercase

[: Alpha:]: Uppercase and lowercase letters

[:d igit:]: Number

[: Alnum:]: Numbers and uppercase and lowercase letters

# Man 7 Glob View details

[[: Alpha:]]*[[:space:]]*[[:alpha:]]

Letters start and end with white space characters in the middle

[^]: matches any single character outside the specified range

[^[:space:]]: The text does not contain blank

Displays all files that end with a number and do not contain white space in the file name

LS *[[^:space:]][0-9]?????

⑩

User's permission location

Tom:ls

Rwxr-xr-x Root Root/bin/ls

LS can be executed, depending on the initiator Tom

Tom first compares with the user owner to see if they are in the same group as the owning group, otherwise it is someone else.

11.

Encryption Method :

Symmetric encryption: Encrypt and decrypt using the same password

Public Key cryptography: each password appears in pairs, a private key is a public key

One-way encryption, hash encryption: Extracting data signatures, often used for data integrity checks

1, the avalanche effect to prevent reverse engineering

2, fixed-length output

Fixed-length output of md5:message digest,128 bit

Sha1:secure Hash algorithm,160 bit fixed length output

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Linux Common Command points