bash scripting basics

, 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 error redire

detecting a file name provided by the user, we perform a 9 to 1 loop. File 9 is named 10, file 8 is renamed to 9, and so on. After the loop is complete, we name the original file 1 and create an empty file with the same name as the original file.DebugThe simplest debug command, of course, is to use the echo command. You can use Echo to print any variable value in any place where you suspect it is wrong. That's why most shell programmers spend 80% of their time debugging programs. The advantage

as ${name:3:2}: Discard 0-2 of the array variable, only take the 3,4 array variable;Undo Array:Unset Array_NameTo delete an element in an array:Unset Array_name[index]Random variable: Can produce a set of stochastic variables between 0-32767Cases[Email protected] ~]$ echo "$RANDOM"16952[Email protected] ~]$ echo "$RANDOM"6653Five. Bash script programmingThere are three types of shell scripting:Over-programming languagesScripting Class programming lan

when the function is executed because the alias substitution defined in the function occurs when the alias is read, not when the function is executed, because the function definition itself is a compound command. As a result, aliases defined in the function will only take effect if the function finishes executing. For insurance purposes, you should always place the alias definition on a separate line and not use alias in the composite command.Aliases are useful in some cases, because depending

, then alias execution will directly find the specific file and skip all subsequent searches (that is, keyword->function,-> Built-in-> $PATH). Please keep an eye out for them.Finally, when you do the experimental verification can be divided into 2 types of verification, because a command cannot belong to both keyword and built-in, so you can:　　1) Select a keyword such as while, define a while alias,function, and then write a shell script name for while stored in the path variable at a certain pa

$# The number of arguments passed to the script or function $*/[email protected] All parameters passed to the script or function. When enclosed by double quotation marks (""),[email protected] is slightly different from $* $$ The current shell process ID, which is the process ID for the shell script, which is where these scripts are located Take a look at the following script:#!/bin/bashecho "File Name: $0"echo "First Parame

ENGINEER1.4Shell Script BasicsUnderstanding the shell environmentHow bash shells are usedInteractive:--manual intervention, high degree of intelligence----explain execution by article, low efficiencyNon-interactive:-Need to design in advance, the difficulty of intelligence is big;--Batch execution, high efficiency;-Easy to implement in the background and quietly;What is Shell scripting : Designing executabl

shell scripting Introduction and common Tools Shell Script Shell script: is actually a batch script in Windows, multiple shell command collections that can be executed at once. Scripts on Linux can be implemented in a number of languages, and the bash shell is a relatively simple one, and the higher-order can be used in other scripting language

languages. This begins with what we call the shebang mechanism, and his main function is to tell the system that the file should be executed by the Bash interpreter, followed by the body of the program.The content of the text is what you want to complete, then how to write the text content? The main ideas are as follows: Demand analysis Program Logic Analysis Writing Program Debugging bugs First, let's ta

only numbers, letters, or underscores, and cannot start with a number3, as far as possible to see the name of the ideaVI. Bash configuration files1. Profileclass : Provides configuration for the interactive login shell process.• Valid profiles for all users are globally valid:/etc/profile and/etc/profile.d/*.sh• Only the profile that is valid for the current user is valid for the user: ~/bash_profileNote: The function of profile type configuration fi

script requires a user name list file as a parameter2) If no parameters are provided, this script should give a hintUsage:/root/batchusers, exit and return the corresponding value3) If a nonexistent file is provided, this script should give aShow Input file not found, exit and return the corresponding value4) New User login Shell is/bin/false, no need to set password5) User list test file:Http://classroom/pub/materials/userlist# wgethttp://classroom/pub/materials/userlist[Email protected]/]# vi

results of "mail.jpg tux.jpg".quotation marks (single and double quotation marks) prevent this wildcard extension: #!/bin/shecho "*.jpg" Echo ' *.jpg ' This will print "*.jpg" two times.Single quotes are more restrictive. It prevents any variable expansion. Double quotes prevent wildcard expansion but allow variable expansion. #!/bin/shecho $SHELLecho "$SHELL" Echo ' $SHELL ' The result of the operation is: /bin/bash/bin/

Bash programming Basics I. The origin of Bash 1. What is Bash? shell Bash is GNU Bourne-again shell, which is used by most Linux distributions. Shell is an interface provided by * nix for users. The underlying layer of an operating system runs independently, The user interfa

1. What is Shellscriptshellscript is to use the shell's function to write a "program", the program is to use a plain text file, some shell syntax and commands (including external commands) written inside, with regular expressions, Pipeline command and data flow redirection, conditional judgment statements and other functions, in order to achieve our desired processing purposes. 2. Script or program source files are plain text files. 3. The execution of a script or program is generally done in tw

\vVersion of Bash\vBash release number, version number plus patch level\wCurrent working directory\wBasic parts of the current working directory\!The history number of this command\#Command number for this command\$If the valid UID is 0, that is #, the other case is $\nnnCharacter corresponding to octal number nnn\\A back slash\[The beginning of a non-printable sequence of characters that can be used to embed the terminal control sequence at the promp

article, after receiving the strong support of Mr. Hongbin of Chinabyte Network College, you will be able to see this article. The author earnestly hopes that through this article for the vast number of WEB developers and enthusiasts to provide convenience, to enable everyone to participate in the study and exchange of ASP, in order to cover the needs of readers at different levels the author decided to start from the most basic scripting language,

% $Y 3 · [Email protected] ~]# ycube=expr $Y \* $Y \* $Y [Email protected] ~]# echo $Ycube 4096 · ################### #Position variable #################### represented as $n, n is a number between 1~9 · [Email protected]/]# VI add.sh #!/bin/bash sum=expr $1 + $2 echo "$ + $ = $SUM" · [Email protected] ~]# chmod +x add.sh · [Email protected]/]#./add.sh 12 34 12 + 34 = 46 · ################### #Predefined variable #################### $#: Number of po

article, after receiving the strong support of Mr. Hongbin of Chinabyte Network College, you will be able to see this article. The author earnestly hopes that through this article for the vast number of WEB developers and enthusiasts to provide convenience, to enable everyone to participate in the study and exchange of ASP, in order to cover the needs of readers at different levels the author decided to start from the most basic scripting language,

Starting from the game scripting language, this article analyzes the script basics set up by Mono and the script language mono.0x00 Preface In my daily work, I occasionally encounter the following question: "Why have game scripts become indispensable in current game development ?". So this week I wrote an article about the game script and analyzed why the game script appeared, and what script base does mono

Arithmetic operations are undoubtedly very important in shell scripting programming;The command to perform an integer arithmetic operation in bash is let, which has the syntax format:Let Arg ...Arg is a complete arithmetic expression consisting of a separate arithmetic expression, such as +,-,*,/,%,^;where ^ is the square operation, such as 2^3 represents 2 of the three-time side;The Let command can be over