Getting Started with Shell programming

Getting Started with Shell programming

~/.bash_history//root file path preserving the command history

$HISTSIZE//History command variable

Sleep 100//Sleeping 100

Sleep 200//sleeping 200

CTRL + Z//pause command Run

Jobs//View tasks

FG//Recall front Desk

FG 2//Select a process to be recalled to the foreground

BG//Recall back-office operation

ENV//Display System variables

Set//Show more variables (including env variables and custom variables)

Variable cannot start with a number

Myvim= ' which vim '//anti-quote ' is the result of the reference command

c= "$a"//$a there are numbers that need double quotes "" and will be separated

Input bash enters a child shell, and if you need to use a variable from the previous shell, make a global declaration of export A=1

unset//Cancel the value of a variable

/ETC/PROFILE.D/PATH.SH//Previously defined in the/etc/profile file path is not very good, it is recommended to define under PROFILE.D

Source/etc/profile//reset takes effect,/etc/profile can automatically load all the. sh

/ETC/BASHRC//Definition PS1

Ps1=[\[email protected]\h \w]\$//define command prefixes

Ps1= ' [\[email protected]\h \w]\$ ' again cd/tmp//W to w display only last paragraph

Ps1= ' [\[email protected]\h-\t \w]\$ '//define Time

/etc/profile/umask.sh//define UMASK.SH in this path change umask value

Special symbols

*//With multiple positions

？ Only one

#//Notes

\//de-symbol, remove the original effect

$//To use this variable will be added $

&//Put commands in the background

&&//write two commands together

Cut//Segment

Cut-d:-F 3,4,5/etc/passwd//To: for the separator, the 3,4,5 section is displayed

Cut-d:-F 3,6,5/etc/passwd//To: for the separator, the 3,6,5 section is displayed

Cut-c 10/etc/passwd//intercept 10th character

Cut-c 1-10/etc/passwd//intercept 1-10 characters

Sort//sorting

SORT/ETC/PASSWD//No option to sort by ASCII table

SORT-T:-k3-n/etc/passwd//To: For the separator number, take the 3rd paragraph, sorted by number

SORT-T:-k3,5-n/etc/passwd//To: For the separator number, take the 3rd to 5th paragraph, sorted by the number. Reminder: 3,5 is an interval, meaning 3 to 5. Instead of being represented as 3-5. It's different from cut.

SORT-T:-k3,5-n-r/etc/passwd//To: For the separator number, take the 3rd to 5th paragraph, sorted by the number reverse order.

Sort-u//GO repeat

Wc

-W calculates the number of words

-M calculates the number of characters

-L calculates the number of rows

Uniq to repeat (if two are not to be repeated)

Uniq-c 2.txt//view quantity in-C

Sort 2.txt | Uniq//Sort first and then repeat with Sort-u 2.txt is the same

Tee Redirection and output information displayed on the screen, need to add piping |

echo "1111" | Tee 1.txt//redirect to 1.txt and output information to the screen, overwriting the original data written in 1.txt text

TR Replacement Character

LS *.txt | Tr ' A-Z ' A-Z '//lowercase to uppercase

echo "FASDFASDFASDF" | Tr ' a ' R '//convert individual lowercase to uppercase

Split cutting Large files

Split-b 50m 1.txt; Split-l 1.txt

Split-l anaconda-ks.cfg//Split one file per 10 lines

Split-b anaconda-ks.cfg new_//100b partition a file, add new for the first definition, easy to distinguish, in addition to B, other units to add

&& Reading and

The previous command executes successfully and executes the following command

The preceding command does not execute successfully, and the following command is not executed

|| Or

The command on the right is not executed until the left command executes successfully

Regular expressions

grep filters The specified rows

grep ' root '/etc/passwd//matches to the row

grep--color ' root '-n/etc/passwd//color shows the line and line number to match

Alias CG = ' grep--color '//home directory. BASHRC define Alias

Cg-v ' root '/etc/passwd//not including the root line

Cg-c ' root '/etc/passwd//Total match occurrences

CG ' ^[0-9] '/etc/passwd//This symbol ^ is the line starting with what

CG ' [^0-9] '/etc/passwd//This symbol ^ in parentheses meaning is not the same, meaning is not 0-9, 0-9 excluded rows

CG ' ^$ '/etc/passwd//This symbol $ is blank line

Symbols for regular expressions

. Any single character

*//0 or more * preceding characters

. *//any character of any length

\? 0 or 1 preceding characters

Egrep

+ represents one or more preceding characters, excluding 0

grep--color ' r\?o ' 1.txt = = egrep--color ' r?o ' 1.txt//This symbol \? With Egrep no need to add the characters

Egrep--color ' r+o ' 1.txt//This symbol + denotes one or more preceding characters, excluding 0

Egrep--color ' root|nologin ' 1.txt//This symbol | Yes or this or that.

Egrep--color ' (RR) + ' 1.txt//This symbol () represents the whole

Egrep--color ' (RR) {1,3} ' 1.txt//specified number of times

sed function is to print, match, delete

Sed-n ' P 1.txt//print line 10th

Sed-n ' 1,10 ' P 1.txt//Specify range 1 to 10 rows

Sed-n ' 30,$ ' P 1.txt//30th line to Tail line

Sed-n '/root/' 1.txt//print the line containing the root

Sed-r-N '/(R) +/'//Plus option-r no need to add the caret

Sed ' ^$ ' d 1.txt//Remove blank line, not really deleted, just display to screen

Sed-i ' 1,19 ' d 1.txt//plus-i option is really deleted

SED replacement

Sed ' 1,10s/nologin/login/g ' 1.txt//replace Nologin directly with login

Sed ' s/nologin/login/g ' 1.txt//s replace the global nologin with login

Sed ' s#.*$ #login #g '//All lines are replaced by login

Sed ' s#.*$#&login#g '//All lines at the end plus login, need to use &

Sed ' s#[a-za-z]# #g '//Remove all characters

Sed-r ' s# (^[a-z]+) (:. *:) (. *$) #\3\2\1#g ' 1.txt//replace the preceding character with a later character

Sed-n '/root/p; /aming/p ' 1.txt = sed-n-E '/user/p '-e '/aming/p ' 1.txt//This expression can write multiple statements

Awk

Segmentation

Awk-f ': ' {print $} ' 1.txt//-f Specifies delimiter: segment display, but display will be delimited by spaces

Awk-f ': ' ofs= ': ' {print $3,$4} ' 1.txt//-f Specify delimiter: Segment display, but display will be separated by a space, adding ofs= ":" is displayed with: delimiter

The

awk '/user|boot/' 1.txt//match user or boot

Awk-f ': ' $1~/r*o/' 1.txt//in $ (the first paragraph) contains/r*o/will be matched

Awk-f ': ' $1~/r*o/{print $} ' 1.txt//in $ (the first paragraph) contains/r*o/will be matched to show only the third paragraph during the matching process

Awk-f ': ' $1~/r*o/{print $1,$3}; $1~/user/{print $1,$3} ' 1.txt//multi-segment matching

Conditional operator

Awk-f ': ' $1== ' nobody ' 1.txt//$1= ' nobody ' segment matches

Awk-f ': ' $3>=500 ' 1.txt//$3>=500 segment matches out

Internal Address variables

Awk-f ': ' nr<10 ' 1.txt//Print out the first 9 lines

Awk-f ': ' nr==10 {print $1,$7} ' 1.txt = = Awk-f ': ' {if (nr==10) print $1,$7} ' 1.txt//Print out the first 10 lines and print the specified segment

Awk-f ': ' {if (nf==7) print NF $ ' 1.txt//Match segment

Awk-f ': ' {(sum=sum+$3)}; END {print sum} ' 1.txt//sum of all segments

Getting Started with Shell programming