bash shopt

First of all, in the bash script, there are three kinds of quotes 1. Single quotes '2. Double quotes "3. Inverted quotes ' Single quotation markThe two string enclosed in single quotes is an ordinary string that retains its original literal meaning.Double quotesTwo strings enclosed in double quotes, and some special characters will act on them.These special characters are: Dollar sign $, backslash \, inverted quotation mark, exclamation point!.Inver

Beijing Time September 25 news, Linux users today again got a "surprise"! The Red Hat security team found a cryptic and dangerous security breach in a widely used bash shell in Linux. This vulnerability is referred to as "Bash bugs" or "Shellshock". When the user is properly accessed, the vulnerability allows the attacker's code to execute as if it were in the shell, which opens the door for a variety of a

Write robust Bash scripts many people use shell scripts to complete some simple tasks and become part of their lives. Unfortunately, shell scripts are greatly affected when an exception occurs. It is necessary to minimize such problems when writing scripts. In this article, I will introduce some simple tasks that let bash... write robust Bash scripts. many people

Bash environment configuration file Do you think it's strange that we didn't do anything, but we got a bunch of useful variables as soon as we got into Bash? This is because the system has some environment configuration file cases, so that Bash can directly read these configuration files at startup to plan the bash o

Ubuntudash Shell Https://wiki.ubuntu.com/DashAsBinSh Http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_title.html From Ubuntu 6.10, dash (theDebian almshells) is used by default instead of bash (the GNUBourne-Again Shell ). but Login Shell is still bash. the reason is that dash is faster and more efficient, and it complies with POSIX specifications. Ubuntu runs a lot of shell scripts during star

/bin/shwith /bin/bash the distinction, the : intercept string is not POSIX standard.Difference shGeneral set bash of soft chains (symlink)[plain] view plain copy print? Ls-l/bin/sh lrwxrwxrwx 1 root root 4 Sep 04:45/bin/sh, Dash In a generic Linux system (exceptions FreeBSD , OpenBSD etc.), using sh the call execution script is equivalent to

Files related to bash environment settings include: /Etc/profile (main) $ Home/. bash_profile (main) $ Home/. bash_login $ Home/. Profile $ Home/. bash_logout (main) $ Home/. bashrc (main) /Etc/bashrc Description:* Login# Run/etc/profile first# Bash then checks whether. bash_profile,. bash_login, or. profile exists in the user's own directory. If yes, bash execut

Bash usage SummaryIn Linux, shell is basically bash by default. Below are some tips I have summarized. Background running programs() Use a sub-shell, such as (cd.../../commlib/; make)$ () Command replacement, same''Example:For example, you need to use the awk script in the shell script.Awk-f /Abc /{Print $0;}EOF) $ () Perform integer calculation $(66/2 ))If (arithmetic operation )) If [[String operation] Al

/bashDeclare-I sum = 0For I in {1 .. 100}; doIf [$ [$ I % 3]-eq 0]; thenLet sum + = $ IFiDoneEcho "the sum is: $ sum" 2. Calculate the sum of all odd numbers within 100 and the sum of all even numbersCopy codeThe Code is as follows :#! /Bin/bash# Echo "exercise"Declare-I sum1 = 0Declare-I sum2 = 0For I in {1 .. 100}; doIf [$ [$ I % 2]-eq 0]; thenLet sum1 + = $ IElseLet sum2 + = $ IFiDoneEcho "the even sum is: $ sum1"Echo "the oddnumber sum is: $ sum2"

Bash (GNU Bourne-again Shell) is a Unix shell written for the GNU program, which is the default shell used by many Linux platforms.Variables for bash scripting:1. $BASHRepresents the path of a bash binary program fileEg: Edit the bash file, such as 1.sh, in which the following code is entered:Then save the run and the

Looping: Performing a loop body code 0, 1, or moreEntry conditions: Conditions for entering the cycleExit Condition: Condition of the circular terminationFor loop:For VARIABLE in LIST; DoLoop bodyDoneExample 1: Write a script, create 20 users, and give the user a user name as a password#!/bin/bash#for user in user{1..10};do if ID $user; Then echo, "User is exists." else Useradd $user echo "Add user $user finished." FidoneExample 2: Write a script to s

Yesterday, a person on the Bug-bash asked: why [--help did not output help information. Someone answered him because coreutils provided the [command to accept the--HELP option, and Bash's own [command does not accept any options.] When you execute [--help ] in Bash, of course the first priority is the internal command [, not the external command [, the execution of /usr/bin/[--help(on my Mac is/bin/[) to ge

1. what is the shell Operating System Interface? through shell, you can call the corresponding hardware through the kernel. 2. what is Bash? BourneAgainSHell (bash) is actually a version of shell. 3. BashShell functions: 1) command compilation (Command history);... 1. what is shell? The operating system interface. the shell can call the corresponding hardware through the kernel. 2. what is

SummaryPreviously written to see other people write scripts with SHC encryption, I also have to understand the next.SHC represents shell script compiler, the shell scripting compiler. A script that has been compiled by SHC is not readable to ordinary users, so if you want to protect your code (for example, with a key), you can consider SHC; however, some people can use the reverse compiler to crack the SHC encrypted script.Let's start by introducing:I. Using SHC to encrypt

ArrayWhat is an array?An array in a computer refers to a data type that is organized in a certain order by a number of variables of the same type.The popular point is that the array is one of the variables, in terms of the current term is a variable circle, but this variable circle is the same type of variables and have a certain organizational order.Format of the arrayArray[key]=valueArray: Represents the name of the array variableKey: Indicates the index of the array element is also called sub

ArrayWhat is an array?An array in a computer refers to a data type that is organized in a certain order by a number of variables of the same type .The popular point is that the array is one of the variables, in terms of the current term is a variable circle, but this variable circle is the same type of variables and have a certain organizational order.Format of the arrayArray [key]=value array: represents the name of an array variableKey: indicates that the index of an array element is also call

What is Bash shell script programming?A: There are multiple shells in Linux, and the default shell for CentOS and Redhat is the bash shell. As for shell scripts, this is a bit like (. bat file) for batch files inside the Windows operating system. I wonder if you remember the philosophical thinking of Linux? There are two points: a single application consisting of a multitude of purposes: A program that only

Original URL: http://www.mike.org.cn/articles/linux-linux-bash-command-search-mechanism/Turn from: Eric cheung:linux (BASH) command search mechanismThis article assumes that the environment is gnu/linux, and that the shell is bash;　　Note: In addition, we discuss the premise that when you type a command and do not specify the path of the command, for example, we t

First, the variable name1, can only contain letters, numbers and underscores, and cannot start with a number,2. Should not be the same as the existing environment variables in the system3, the name to have the meaningIi. Assigning values to variablesVariable name = value Var_name=value equal to no space on either side[email protected] ~]# Name=Jerry~]#echo $NAMEjerryThird, bash: variable type1. Environment variablesThe script starts a child shell pro

Tags: cin technology share Microsoft-O-Clear CTO SOF Ant 1.5Often heard: Shell programming, bash programming, and bash shell programming, what is the shell, and what is bash, what are the links between the two ... bourne shell is the shell used by the early Unix system, located in/bin/sh, or SH, which is the shell's embodiment. It can be understood that the