bash shell scripting tutorial

"array is:" ${lengthn}#Shell Pass Parametersecho "Executed file name: $"echo "First parameter: $ $"echo "The second parameter is: $"#Shell operator: Native bash does not support simple math operations, but can be implemented with other commands, such as awk and expr,expr, which are most commonly used.#expr is an expression calculation tool that uses it to perfor

direct input MySQL password on the command line above), then your host can be nerve-racking! Is it better to record more or less commands? This part is a matter of opinion, there is no definite answer.Command and file completion features: ([tab] key Benefits)[Tab] is followed by the first word of a sequence of commands, then the command is complete;When [Tab] is next to the second word of a string of commands, it is "file completion"!Command alias Configuration feature: (alias)You can enter ali

multi-tasking purpose!Programmatic scripting: (shell scripts)In the DOS era, remember the so-called "batch file" that writes a bunch of commands together? The shell scripts under Linux is a more powerful feature that allows you to write a sequential command that is often required by your management system as a file that can be used to detect the host in a intera

Many people may have thought about using PHP to write some programs such as timed sending, but they have no way to implement PHP on a regular basis. This article was invented once when I went to PHPBuilder, so I want to translate it for you (and make some corrections at the same time). I hope many people may have thought about using PHP to write some programs such as regular sending, but they have no measures to implement PHP on a regular basis; I invented this article when I went to PHPBuilder,

Shell Programming:Bash:#!/bin/bash must be specified at the beginning of the shellHow the Shell executes:1../1.sh executes the 1.sh,1.sh in the current directory if the executable file2. bash/usr/local/1.shDefine variable aa= ' QQQ ' = cannot have spaces on either side, use variable ${AA}

Tags: operator ace error brings Roo company Operation RorWhen scripting is often written in operations, most people first think of using "-eq" for comparisons when using variables intermittently, but in fact if the variable value is null (NULL) for a special reason, bash shell converts null to 0 for "-eq" comparison, if you encounter this kind of confusion, you c

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/82/94/wKiom1dbsIGDuCnRAAH8FIk-588267.png "title=" QQ picture 20160611143136.png "style=" Float:none; "alt=" Wkiom1dbsigducnraah8fik-588267.png "/>Shell script: Data batch processing, Task batch processingThe shell script file is suffixed with. SH, which is practically meaningless.Shell Operating principle:1. Command Relay (Create sub-process, parse

"idempotent", and in shell scripts it is necessary to use a large number of program logic to determine whether a command satisfies its operating conditions to avoid serious errors during operation;Code content in a shell script1. The first line must be shebang, the interpreter path, must occupy the absolute beginning, when executing, launches the corresponding interpreter to explain the script many command

environmental changes to the parent shell. 2. Use parentheses () Running a command in () also opens a child shell. So do not randomly write () in Linux to change the priority, unless it is escaped, and the parentheses after the turn to have a space between the contents of the parentheses. [Email protected] tmp]# echo $BASH _subshell 0 [Email protected] tmp]# (ec

the exponentiation is ^ implementation arithmetic: (1) Let var= arithmetic expression (2) var=$[arithmetic expression] (3) VA r=$ (arithmetic expression)) (4) var=$ (expr arg1 arg2 arg3 ...) when multiplying to translate *, i.e. \* (5) declare–i var = value (6) echo ' Arithmetic expression ' | BcPractice:1. Write script/root/bin/sumid.sh, calculate the sum of the 10th user and 20th user ID in the/etc/passwd file [[email protected] bin] #vim sumid.sh #!/bin/