Linux Shell Learning

Shell Features:

History is saved in ~/.bash_hostory and retains 1000 records: defined in

Echo $HISTSIZE

!: Previous Command

!$: Last parameter of previous command

! 950: No. 950 order

!c: The most recent command in history that starts with C

TAB: Command completion

Alias: Aliases Unalias

*,?: Wildcard Regular expression

|: Pipe character

>,>>: Redirect and append

2>: Error redirect 2&1>: Neat and bad redirect

Add a numeric ID to the back of the SLEEP,FG,BG,JOBS:FG

Shell variables:

ENV: View System variables

Set: System and custom variables

Variable with special characters, need single quote: b= ' ls/tmp '

Variables in the reference command, using the anti-quote: myvim= ' which vim '

The connection between variables, in double quotes: c= "$a" 12

Export: Variable Global declaration

Local: Variable partial definition

unset d: Delete the value of a variable

Shell Environment variables:

System level:

/etc/profile:/etc/profile.d/*.sh

/ETC/BASHRC:

1)/etc/profile.d/*.sh

2) ps1= ' [\[email protected]\h-\t \w (w)]\$ '

3) Umask Modification

Umask.sh:umask 0012

User level:

. Bash_history: Record History commands

. bash_logout: What to do when you exit

. Bash_profile: User's own environment variable configuration file

. bashrc:root aliases used by users

Shell Basic usage Cut:

cat/etc/passwd | Cut-d ': '-F 1 | Head-n5 (to: first 5 pieces of data of the split)

head-n2/etc/passwd | CUT-C2 (interception of the second character)

head-n2/etc/passwd | Cut-c1-5 (intercept 第1-5个 characters)

Shell basic usage of sort:

head-n5/etc/passwd | Sort: Ascending

head-n5/etc/passwd | SORT-T:-k3-n: Sort with a third field using pure numbers

head-n5/etc/passwd | SORT-T:-k3,5-r: Reverse-sorts strings from third to fifth fields

Cut-d:-f1/etc/passwd | Sort-n-u:-nu will treat the string as 0 and go back to

WC for basic Shell usage:

Wc-l 1.txt 2.txt: Lists a few lines

Wc-w (Word): Outputs how many words are separated by a space

echo "12345" | Wc-m: How many characters are output

Shell basic usage of uniq and tee:

Uniq + files: de-weight

Sort + Files | Uniq-c: Only the two rows are identical to each other, and C is the number of rows that can be counted.

echo "1213" | Tee + Files: Redirect and display the results on the screen

The Shell's basic usage tr and split:

head-n2/etc/passwd | TR ' [A-z] ' [A-z] ': Convert lowercase to uppercase

-D: Remove a character;-S: Remove duplicate characters

split-b500 passwd: The file is divided into 500bytes as a file, the default does not specify the target file, it will produce xaa,xab,xac ... File to display

Split-l 10 + file: Split the file in 10 behavioral units

Split-b 500 + file 123: Specify the target file name, the 123aa,123ab,123ac ... To display

The Shell basic usage of grep:

Grep:

1). -C: Print the number of lines that meet the requirements

2). -N: Output line number

3). --color: Display Color

4). -V: Print rows that do not meet the requirements

5). -a+ numbers: Displays rows that meet the requirements and the following n rows

6). -b+ Number: Displays the line that meets the requirements and the top n rows

7). -c+ Number: Displays the line that meets the requirements and the top and bottom n rows

8). -RH: Access directory Grep-rh "Iptables"/etc/*

9). --include: Include a file

Filter all the lines in the *.php document that contain eval in a directory

Grep-r--include= "*.php" ' eval '/data/

Egrep = Grep-e

SED basic usage of Shell:

Sed ' p-n 1.txt: Plus-n prints out rows that match the rules

Sed-n '/root/' p 1.txt: Print lines that contain special characters

-r:sed does not recognize +| Symbols such as {} () need to be de-defined characters \ or-R

Sed-n-R '/ro+/' P 1.txt

Sed-n '/ro\+/' P 1.txt

-E: Implementation of multiple tasks, can also be used; To achieve

Sed-e '/root/p '-e '/body/p '-n 1.txt

D: Delete the specified line

Sed '/root/d ' 1.txt; Sed ' 1d ' 1.txt; Sed ' 1,10d ' 1.txt

S: replace

Sed ' 1,2s/ot/to/g ' 1.txt

Replaces the position of two strings, where \3\2\1 represents three () of the contents

HEAD-N2 1.txt | Sed-r ' s/(Root) (. *) (bash)/\3\2\1/'

A: Add after the specified line

Sed ' 2,4a abcd ' xx.txt add ABCD in 2 to 4 rows

-I: Modifying files directly

Sed-i ' s/ot/to/g ' 1.txt

The basic Shell usage of awk:

1. Awk-f ': ' {print $} ' 1.txt

2. Awk-f ': ' {ofs= ' # '} {print $1,$2,$3,$4} ' 1.txt is

Awk-f ': ' {print $1#$2#$3#$4} ' 1.txt

3. awk '/oo/' 1.txt: Match oo

4. Awk-f ': ' $ ~/oo/' 1.txt: Match oo in the first paragraph

5. Conditional operator ==,>,<,!=,>=,<=

The third paragraph is 0:awk-f ': ' $3== ' 0 "' 1.txt

The third paragraph is greater than or equal to 500:awk-f ': ' $3>=500 ' 1.txt

The seventh paragraph is not '/sbin/nologin ': awk-f ': ' $7!= '/sbin/nologin ' 1.txt

6. Awk built-in variable NF (number of segments) NR (number of lines)

Head-n3 1.txt | Awk-f ': ' {print NF} '

7. Mathematical calculations:

Awk-f ': ' {ofs= ': '}{$7=$3+$4; Print $} ' 1.txt

8. Awk-f ': ' {(tot=tot+$3)}; END {print tot} ' 1.txt

9. Awk-f ': ' {if ($1== "root") print $} ' 1.txt

Shell Basic Syntax:

1) #!/bin/bash specified to run with bash

2) If statement

if condition; Then

Command

Fi

if condition; Then

Command

Else

Command

Fi

if condition; Then

Command

Elif condition; Then

Command

Else

Command

Fi

3) [Conditions]

-D: Whether it is a directory

-F: is normal file

-L: Is the connection file

-E: whether there is

-N: Not 0

-Z: Whether it is 0

-R (-w-x): whether there is permission

4) for And while

For i in ' SEQ 1 5 ' Do

Echo $i

Done

While condition; Do

Command

Done

Dead Loop:

While:; Do

Command

Sleep 3

Done

Continue Break Exit

5) Date Command

1) 2015-08-25:date +%y-%m-%d

2) 15-08-25:date +%y-%m-%d

3) Date +%f

4) 21:45:15:date +%h:%m:%s

5) 21:45:15:date +%t

6) Timestamp: Date +%s

7) date-d @1440510413

8) After one day: date-d "+1day"

9) One day ago: date-d " -1day"

10) January ago: date-d " -1month"

11) One minute ago: date-d " -1min"

12) Week: Date +%w (%w) lowercase for weeks, uppercase for week of the year

6) Mathematical operations

sum = $[$a + $b] (+-*/)

Decimal: Echo "SCALE=2;10/3" | BC Output 3.33

7) Interaction

Read-p "Please input a number:" X

8) Sh-x xx.sh View the execution process

9) Case Syntax

Case variable in

value1)

Command

;;

value2)

Command

;;

*)

Command

;;

Esac

) Shell Array

A= (1,2,3,4)

Number of array elements: Echo ${#a [@]}

Read single element: Echo ${a[2]}

Print the entire array: Echo ${a[@]} or echo ${a[*]}

Delete array: unset a unset a[1]

Array shard: Echo ${a[@]:0:3} from table 0 below 3

Array substitution: Echo ${a[@]/3/100} change the array to a third 100

Linux Shell Learning