bash amplifier

Understanding and learning bashtable OF CONTENTS 1. Understand bash 2. Shell Variable Functions 3. Command alias and History commands 4. bash shell operating environment 5 Data Stream redirection 6 pipeline commands 1 Understanding bash Use shell to communicate the input commands with the kernel so that the kernel can control th

Arithmetic Operations in Bash: Operators +,-, *,/, and % Declare: -I: integer variable -X: environment variable, similar to export 1. Let: performs arithmetic operations in the format of let varname = arithmetic expression If the calculation result is decimal, the fractional part is omitted. For example, let sum = 4 + 1 and the result is 5. Echo $ sum Let s = 16/3, the result is 5 Echo $ s 2. varname = $ [arithmetic expression] 3. varname = $ (arithm

Hive hql: from a string "P? A? B? C? PPP? Hhh "? As the separator, find the 5th string Bash program: Test. Sh#!/bin/bashhive -e "select (split('p?a?b?c?ppp?hhh','?'))[4] from a limit 1;"Error:Caused by: Java. util. RegEx. patternsyntaxexception: dangling meta character '? 'Near index 0 is changed:Test. Sh#!/bin/bashhive -e "select (split('p?a?b?c?ppp?hhh','\\\\?'))[4] from a limit 1;"Reason for correct running:The second parameter of split is a RegEx,

Bash is a Linux-based shell, and many of the commands described in the front are handled by Bash's environment. Here's a general-to-local understanding of bash. For bash I've roughly divided it into three parts: variables, the configuration of the operating environment, and the output of commands. The summary of Bash d

This problem occurs because there is no configuration. Bash_profile problem, or we accidentally emptied or deleted the. bash_profile file.Method One: Modify the ~/.bash_profile fileThe steps are as follows:Vim ~/.bash_profile(No tube. Bash_profile This file has a few, you can create a new one is also possible)At the end addExport ps1='[\[email protected]\h \w]\$'And then executeSOURCE ~/.bash_profileThis way the shell can display the path.Method Two: Copy the new user to the root user-

Login Linux The system command prompt appears as: -bash-4.1$1. Description of the problemLogin Linux The system command prompt appears as follows: -bash-4.1$-bash-4.1$ 2. Cause Analysisconfiguration file for user-related environment variables . BASHRC and bash_profile. 3. Workaround/etc/skel when a new user is createdthrough the Useradd

Linux Summary bash features Command history: Use command: History Environment variables: Histsize: The number of bars recorded in the command history buffer, which defaults to 1000; Histfile: Record the current logged-in user logout the history command to store files; Histfilesize: Command history file records the number of history, the default is 1000; Operation Command History:

Bash featuresTerminal, the interface program attached to the terminal:Gui:kde, GNome, XFCECli:/etc/shellsBashZshFishFeatures of bash:Command line expansion: ~, {}Command aliases: Alias, UnaliasCommand history: HistoricalFile name wildcard: GlobShortcut keys: Ctrl + A, E, U, K, lCommand completion: $PATHPath Completion:Bash features: command hashCache the results of previous commands: Key-valueKey: Search KeyValue: ValuesHash command:Hash: Listhash-d C

Features of bash in the shellFeatures of bash in the shellOne of the bash features: command line expansion　　The mechanism of automatically replacing a given special symbol of a command line with another stringDirectory:　　Command: CD "Built-in command"　　Working directory: The directory that is currently locatedCd:change directory (switch directory)CD target path (

Let's review the usage of the last section redirect:1. Quickly empty filesCat Demo.txt Note: Linux has a classic saying "Everything is a file",/dev/null can be considered a special empty file, more image point, can be understood as a sci-fi film in the black hole, any information to the output to it, there is no return, of course, there is no information in the black hole can come out.In general, the above meaning is the use of /dev/null There are other uses, such as using it to let nohup do not

The definition format of the 1:bash function [Function] funname [()]{action; [return int;]}Description1: Can be defined with function fun () or directly fun (), without any parameters.2: The function returns a value that can be returned with a return, or, if not, the result of the execution of the last line of the function body as the return value. Return followed by a value of 0-255. After calling the function, the return value is obtained by $

Ubuntu and Debian's shell are installed by default to dash, not bash.Run the following command to view the details of SH and confirm which program the shell corresponds to:$ls-al/bin/shDash is lighter and faster than bash. But bash is more common.If some commands, scripts, and so on are not always executed properly, it may be the cause of dash.For example, when compiling the Android source code, if you use

The Linux shell is basically bash by default, and here are some of the tips I've summed up. ${varible##*string} The string ${varible#*string after the last string is intercepted from left to right ${varible%%string* the string after the first string from left to right The string ${varible%string* after the last string from right to left intercepts the string after the first string from right to left Background Run programs () use a child shel

default; My blog: Code encyclopedia: www.codedq.net; amateur grass: www.xttblog.com; love to share: www.ndislwf.com or ifxvn.com.-Icon Component (addition icons): Choose whether to create a Quick Launch bar icon or create a desktop shortcut;-Desktop Browsing (Windows Explorer integration): Browse the source method, separate context browsing using only bash or git GUI tools only; The advanced context browsing method uses Git-cheetah plugin plug-ins;-A

Shell--command parser, also a programming languageBash-a specific instance of the shell, zsh, bash are instances of the shell The "Echo $SHELL" command can be used in the terminal to view the shell instance currently in use and can be switched to zsh or other shell instances through "Chsh-s/bin/zsh" . Global profile (all in/etc/directory, etc for Environment config abbreviation): /etc/profile (not recommended)--each user is called at logon /ETC/BA