bash getopts

Linux: circular statement usage in bash Programming 1. if is a single branch statement in the following format: ifcondition; thenstatement hellip ;.. fi2.if hellip; else is a dual-branch statement in the following format: ifcondition; thenstatement hellip ;. elsestat Linux learning path: circular statement usage in bash programming 1.if is a single branch statement in the following format: if condition;

support tools! Of course, if your hardware is too new and your kernel does not support it, I'm sorry, how powerful is your Shell capability, and there is no way to make the hardware work! Can this be understood? Haha! That's right! It is the core task to make the computer host work, but the core of the operation is to work for the user, but it is shell! Therefore, when your shell has been around for a long time, but the hardware cannot work, please note that your "core" is correct? Ah! Far away

Bash Programming: Exercises1. Write a script: If a path does not exist, it is created as a directory, otherwise it is present, and the content type is displayed#!/bin/bash#baseurl=/var/tmp/testdirif [-e $baseurl]; Thenecho "file is no exists." Elsemkdir-p $baseurlfile $baseurlfi2. Write a script to complete the following functions; Determine the given two values, whichever is smaller; method of a given numb

weak type, interpreted type1, do not declare, direct reference2, participate in the operation, automatic conversionTypes of variables (by bash scope)Local Variables the effective scope is the life cycle of the current shell , which is not valid for Shell processes other than the current shell and for the child or parent processes of the current shell . environment variable effective scope The current shell process and its child shell processes are no

weak type, interpreted type1, do not declare, direct reference2, participate in the operation, automatic conversionTypes of variables (by bash scope)Local Variables the effective scope is the life cycle of the current shell , which is not valid for Shell processes other than the current shell and for the child or parent processes of the current shell . environment variable effective scope The current shell process and its child shell processes are no

1. Legal shell and/etc/shells functions shell has multiple versions, including Bourne Shell (SH), C shell, K-Shell, tcsh, etc. Normally Linux uses the Bourne Again Shell (Bash), which is the enhanced version of SH can check/etc/shells to see how many shells are available. Writing a legitimate shell to a/etc/shells file is a way for some of the system's services to check the shells that the user is able to use during the run. When the user logs in,

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

/bin/bash (the Linux preset shell, the default shell in many Linux distributions today, combines many of the advantages of other shells.) )/bin/ksh (KornShell by the T-Bell Lab. Developed, in combination with bash)/BIN/TCSH (Consolidated C Shell, provides more features)/BIN/CSH (has been replaced by/BIN/TCSH)/bin/zsh (based on Ksh developed, more powerful shell) now the general shell is used by

/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