bash scripting basics

advance, and when this function is called, all commands in the function are executed. The shell functions are defined in the following way:[function] Name () {Compound-command} [redirection]This allows you to define a function named "name". The reserved character function is optional. If we give this function reserved word, the parentheses are optional. The body of a function is a compound command. Those commands are usually contained in a compound command between "{" and "}". The entire compou

of the while loop is usually controlled by a variable, which changes the value of the variable in the loop body so that it exits at the appropriate time and avoids getting into a dead loop.The syntax structure of the while loop is as follows:While condition testDoCommand sequenceDonesteps:Step One: Batch Add user account Stu1-stu20Added account has a fixed prefix stu (can be set in practice), multiple accounts starting from 1 numbers, such as STU1, STU2, Stu3 、......、 stu20. --Write script uadd

2017-10-27linux Basics (9) Bash basic featuresIn the previous chapter we talked about FHS, as well as some of the features of command and Bash command history, FHS is the standard filesystem hierarchy, which specifies the classification of the file system to be stored, so that the distribution of the various Linux to get the reference and unity, then we introduce

seconds, in the shell script of the usual term loop.At this point, you press CTRL +z to pause it, and then enter BG to go back into the background.In the case of multitasking, if you want to move the task to the foreground, FG is followed by the task number and the task number can be obtained using the jobs command.9. >>, 2>, 2>> : The above-mentioned directional symbols > and >> denote the meaning of substitution and addition, then there are two symbols which are 2> and 2>> here. Indicate erro

$ ((EXPRESSION))Bash command exit and exit status codecommand is executed at the end of the execution in bash, it can be logged by exiting the status codeThe exit status code of the script depends on the last command executed, and the custom exit status codeExit #: #代表数字Example: Exit 5Run echo $ After this command exits the program and returns 5Success: 0Failed: 1-255Note: Exit the script early, or you can

for inch {1.. 6 }; Do -x echo $i +xdone echo " Script executed "########### #break#!/bin/Bash while : Do Echo-N"Input A number between 1 to 5:"Read Anum Case$aNuminch 1|2|3|4|5)Echo "Your number is $aNum!" ;; *)Echo "You does not select a number between 1 to 5, the game is over!"Break ;; Esac Done############# #case#! /bin/BashEcho 'Input A number between 1 to 4'Echo 'Your number is:\c'Read Anum Case$aNuminc

1. Linux Scripting Basics1.1 Basic Introduction to grammar1.1.1 StartThe program must start with the following line (must be placed on the first line of the file):#!/bin/shThe symbolic #! is used to tell the system that the parameters behind it are the programs used to execute the file. In this example we use/BIN/SH to execute the program.When you edit a good script, you must also make it executable if you want to execute the script.To make the script

line: $ cd /Users/xiaoa/test 11. Enter the $ bash command in Bash to start a subbash program and exit the subprogram with the $ exit command. 12. Command combination and priority execution Enclose the command with a single quotation mark (that is, the key on the left side of the number key 1 above the keyboard, not a single quotation mark): Begin command Or $ (command) to first execute a command, and then

"pleaseinputa ipv4addr: "addrping-W2-c2 $addr >/dev/nullecho "Thisipv4addrcanbeaccess" | | echo "Thisipv4addrcannotbeaccess" 10, determine whether each partition space of the hard disk and inode utilization is greater than 80, if yes, Email notification root Disk full #!/bin/bash#for Iin ' df|grep ' ^/dev/sd "|cut-c45-46 ';d o echo $I if[ $I -ge 80];thencat/etc/ issue|mail-s "Warning,pleasenoticeyousick" test echo "Successful" fidone forIin ' df-i|g

Bash CookBook (1)-basics, bashcookbook Bash was written by brian Fox in January 10, 1988 out of Richard Stallman's suggestion. 1. Run the template: Interactive Login shell, bash reads and executes/etc/profile after login. Then read ~ /. Bash_profile ,~ /. Bash_login ,~ /. Profile, the first executable is found to

redirect error is generated. If Word expands to "-", the file descriptor n is closed. If n is not specified, standard input (file descriptor 0) is used.[N]>wordThis operator is also used to copy output file descriptors. If n is not specified, standard output (file descriptor 1) is used. If a number in Word does not specify a file descriptor to be used for output, a redirect error is generated. In special cases, if n is skipped, and word is not expanded to one or more numbers, standard output an

host.Usage:4Fc–lReadPurpose: Reads a row of data from a standard input.Usage: Read variableCase:Echo ' Please enter your English name? ‘Read ynameEcho ' Your name is: '$ynameIf you do not specify a variable to receive data after the read, the default variable name is replyEcho ' Please enter your English name? ‘ReadEcho ' Your name is: '$REPLYThe same can be achieved by using the READ–P approach:Read–p ' Please enter your English name? ‘Echo ' Your name is: '$REPLYOption-P refers to the meaning

state$?: Saves the execution status return value of the previous command. Success for: 0, others for failureStatus: 1, 2,127: Command error. System reservation.Output redirection:> Overwrite redirects>> Chasing heavier orientation2> Error Overwrite redirect2>> Error Append redirect> simultaneous redirectionOutput redirection has a special location in the/dev/null: bit bucket. The data black hole can output any information inside.ID student >/dev/null The result of the command, regardless of the

declaring environment variables:Export VARNAME (exported, can be applied to all child shells)Export Varname=valueExample[[email protected] ~]$ exportb= ' Hello '[Email protected] ~]$ echo $bHello[Email protected] ~]$ bash[Email protected] ~]$ echo $bHello[Email protected] ~]$ declare:-A: Declaring an indexed array (if supported)-A: Declare associative arrays (if supported) -I : declare shaping variables;-L: Declares the variable and converts the val

Basics of Linux Shell scripting here we first talk about the shell of the basic syntax, the beginning, comments, variables and environment variables, to do a basic introduction, although not related to specific things, but lay the foundation is to learn easily after the premise. 1. Linux Scripting Basics Basic Introduc

profile definition take effect?(1) Re-login;(2) Let the current shell process to re-read the specified configuration file;Source/path/to/somefile. /path/to/somefileNote: It is possible to cause side effectsactual combat:1. Define aliases that are valid for all uses?Answer: just VIM/ETC/BASHRC2. What if only the modification of the PATH environment variable takes effect for the root user?Answer:vim ~/.BASHRC can modify the path variableThis article is from the "Wind Rhyme" blog, please be sure t

Bash Programming Essentialsvariables :Local variable: Valid only for the current shell process, not valid for other shells other than the current shell (including its parent, child, etc.);Environment variables: Valid for Shell processes and their child shell processes;Local variables: Valid only within a certain piece of code space in the current shell process, usually for function local programs;Positional variables: $, $, ... $ is the first paramete

substring: ${string:1:4} #输出下标为1到4的字串, including 1 and 4, Word Poute starting from 0Find sub-string subscript: Echo ' expr index ' $string ' sub_string '[Shell Array]Bash supports one-dimensional arrays (which do not support multidimensional arrays) and does not limit the size of arrays. The subscript of an array element is numbered starting with 0, getting the elements in the array to take advantage of subscript, the subscript can be an integer or a

the other analogy.Please note that if the position parameter n exceeds 9, it is represented by ${n}.$ A represents the name of the executing program.$*.Purpose: Represents all positional parameters and is treated as a string.For example: test.sh ABC 123 xyz, the content of $* is the string "ABC 123 XYZ"[email protected]Purpose: Represents all positional parameters, but [email protected] represents the serial of each positional parameter.For example: test.sh ABC 123 xyz, the contents of [email p

Linux Basics--linux File system and Bash's basic featuresA. linux file system:A file in a Linux file system is a collection of data that contains not only the data in the file but also the structure of the file system, where all Linux users and programs see files, directories, soft links, and File Protection information .Linux file systems follow FHS (Filesystem Hierarchy Standard, File system directory standards), and most Linux versions use this for