Linux Notes General section summary (to be continued)

Linux Notes General section Summary

Shell; child shell

Bash--bash

Bash

1. Command history, Command completion

2, Pipeline, redirect

3. Command aliases

4. Command line editing

5. Command line expansion

6. File name Wildcard

7. Variables

8. Programming

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

Command history:

View command history: Historical

-C: Empty command history

-D OFFSET [n]: Delete command at specified position

-W Save the command history to the history file

Environment variables

Path: Command Search Path

History: Command historical buffer size default 1000 bar

For example:

[Email protected]~] #echo $HISTSIZE

1000

There's a ~/.bash_history in the Ls-a home directory.

The use of command history tips:

!n: Executes the nth command in the command history;

!-n: Executes the reciprocal nth command in the command history;

!! : Execution of the previous order;

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

!$: Reference the last parameter of the previous command

Esc. (Indicates press ESC to release press.)

ALT +. (remote terminal not supported)

Command completion: Command start

PATH:

Path Completion: Path start

Command aliases:

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

Example Alias Cls=clear

Aliases defined in the shell are valid only for the current shell life cycle, and the valid range of aliases is only the current shell process;

Revoke aliases

Unalias Cmdalias

\cmdalias with the command itself

Command substitution: $ (command), anti-quote, ' command '

To replace a subcommand in a command with the process of executing the result

[[email protected] sysconfig] #echo "The current directory is $ (PWD)."

The current directory is/etc/sysconfig.

[[email protected]] #touch./file-$ (date +%f-%h-%m-%s). txt

File-2014-07-21-14-27-36.txt

Quotes supported by bash:

": Command substitution

"": weak reference, can implement variable substitution

': Strong reference, do not complete variable substitution

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-z],[0-9],[a-za-z],[0-9a-za-z]

[: Space:] white space characters

[:p UNCT:] Punctuation

[: Lower:] lowercase letters

[: Upper:] Uppercase

[: Alpha:] uppercase and lowercase letters

[:d Igit:] Number

[: Alnum:] numbers and uppercase and lowercase letters

View Details

# Man 7 Glob

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

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

LS [[: Alpha:]]*[[:space:]][[:alpha:]] Initial white letter

#################################################################

Users, Groups, permissions

Security context (Secure):

Permissions

R, W, X

File:

R: Readable, you can use similar commands such as cat to view the contents of the file;

W: writable, can edit or delete this file;

X: Executable, exacutable, can be at the command prompt as a command to submit to the kernel to run;

Directory:

R: You can perform LS on this directory to list all internal files;

W: Files can be created in this directory;

X: You can switch to this directory using a CD, or you can use Ls-l to view the details of the internal files;

Rwx

r--: Read-only

R-x: Read and Execute

---: No permissions

0---: No permissions

1 001--x: Execution

2 010-w-: Write

3 011-wx: Write and Execute

4 r--: Read-only

5 101 R-x: Read and Execute

6 rw-: Read and Write

7 111 rwx: Read and write execution

755:rwxr-xr-x

Rw-r-----: 640

#############################################################

Users: UID,/ETC/PASSWD

Group: Gid,/etc/group

Shadow Password:

Users:/etc/shadow

Group:/etc/gshadow

User Category:

Admin: ID 0

Normal User: 1-65535 (16-bit 2 binary)

System users: 1-499

General Users: 500-60000

User group Type:

Administrators group:

Normal Group:

System Group:

General Group:

User Group Category:

Private group: When a user is created, a group with the same name as the user name is automatically created if the group to which it belongs is not specified

Basic group: Default group for users

Additional groups, additional groups: groups other than the default group

Process: Tom Tom

Object: rwxtw-r--Jerry Tom A.txt

Tom:ls

Rwxr-xr-x Root Root/bin/ls

This is the security context (77 minutes)

################################################################################

Password file: 7 attributes for a user account

cat/etc/passwd

Whatis passwd View Chapter man document description

Mans 5 passwd

Account: Login Name

Password: password

UID: User ID

GID: Basic Group ID

Comment: note (GECOS)

Home dir: Home directory

Shell: User's default shell

/etc/shadow

Account: Login Name

Encrypted Password: encrypted password

Encryption method: (MD5)

Symmetric encryption: Encrypt and decrypt using the same password

Public Key cryptography: each password appears in pairs, one for the private key (secret key) and one for the public key

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

1. Avalanche effect

2, fixed-length output

Md5:message digest,128 fixed-length output

Sha1:secure Hash algorithm,160 bit fixed length output

SHA256 SHA512

Cases:

Cat/etc/shadow

Syslog:*:16014:0:99999:7:::

Messagebus:*:16014:0:99999:7:::

Sshd:*:16014:0:99999:7:::

Geb:$1$r8jv5.nz$qs5/5kjkv0.qdmglm3h0n1:16014:0:99999:7:::

Second field * or!! Indicates a lock

Third field $r8jv5.nz$ for impurities

Text processing: Cat, more, less, head, tail, cut, sort, uniq, grep

Regular expressions

Pipelines and redirects:> < >> <<

This article is from the "View hardware under Linux" blog, so be sure to keep this source http://4285797.blog.51cto.com/4275797/1585389

Linux Notes General section summary (to be continued)