bash interpreter

BASH command and usage summary, bash usage Summary I need to write a Linux script in my recent work and use a lot of BASH commands. To avoid forgetting it later, I will write them down here one by one. It may be messy. Just take a look. If something is wrong, you are welcome to correct it. 1, export VAR =... This command runs in Shell to make the script that runs

Bash condition test-empty string confusions: bash condition string You can use-n or-z to check whether a string is null. According to the meaning of the operator, if VAR is null or undefined, the-n test result should be false, and-z should be true. Otherwise,-n is true and-z is false. The conditional test list is used, that is, "[-n $ VAR] echo TRUE". If TRUE is output, the conditional test result is TRUE.

In our work, we often need to replace and add URLs from the text using SED. However, we often encounter the ambiguity in the SED of special characters in the URL so that it takes a lot of time to test when writing a bash script. So what are the special characters that create ambiguity? #这些都需要转义, |, \,/, ^, *, (,), [,], {,}, ',? Which, to ",/,?" " for the most important needs to transfer. For example:[Email protected] test]$ url="HTTP://

Bash internal variable learning and Bash variable learning $ SECONDS variable --------- number of SECONDS after the script has been run. Script instance: 1 #!/bin/bash - 2 #=========================================================================================== 3 # 4 # 5 # FILE:seconds.sh 6 #

Linux new user with ssh remote login display-bash-4.1 $, ssh-bash-4.1 There are many methods on Baidu, most of which are in the form of adding PS1 code in. bash_profile, and then logging on to the account again... This method is difficult to achieve the desired results. The root cause of this problem is the lack of Shell environment! [Root @ localhost ~] Su-papi1Last login: Wed Jan 24 04:11:41 EST 2018

0. Interpreter (interpreter) mode definition:given a language, defines a representation of its grammar, and defines an interpreter that uses the representation to interpret a sentence in a language. belongs to the behavioral pattern.The interpreter pattern is rarely used in actual system development because it can caus

Ruby Environment variablesThe Ruby interpreter uses the following environment variables to control its behavior. The ENV object contains a list of all the currently set environment variables.For Unix, use the ENV command to view a list of all environment variables. Hostname=ip-72-167-112-17.ip.secureserver.net rubypath=/usr/bin shell=/bin/bash TERM=xterm histsize=1000 ssh_client=122.169.131.179 1742

There's a question on StackOverflow about the comparison between Java and Python, and there are questions about why Java's runtime is called a JVM, and Python is called interpreter.This problem is estimated not many people think, first look at Wikipedia to see the definition of virtual machine.There are 2 definitions of virtual machines, one is a VMware-like system virtual machine, and the other is a virtual machine called a program virtual machine, such as JVM,CLR, which is the most common virt

StatementIn order to improve the quality of teaching, my college is planning to prepare C language teaching materials. "Write the Interpreter in C language" series of articles after finishing will be revenue book "comprehensive Experiment" chapter. Therefore, the main reading of this series of articles for students who have just finished C language (not requiring data structure and other knowledge), so the wording is more verbose, do not be offended.

SHELL script strategy (learning notes) -- 1.5 bash environment configuration process, -- 1.5 bash From the perspective of user login, shell is divided into two types: Logon shell: If you log on through a terminal, use the su-username command to switch users. Non-interactive shell: for example, you can use the su username command to switch between users. Open the command terminal and shell script in the grap

There are multiple types of Shell in Linux, the most common of which are Bourne shell (SH), c shell (CSH), and Korn shell (Ksh ). Each of the three shells has its own advantages and disadvantages. The Bourne shell is the original shell used by UNIX and can be used on every UNIX. Bourne shell is excellent in shell programming, but it is inferior to several other shells in dealing with user interactions. The default shell in Linux is the Bourne again shell, which is an extension of the Bourne shel

Linux Bash Shell learning notes, bash learning notes Parameter extension: 1. The parameter referenced by the name is called a variable.2. Parameters referenced by numbers are called positional parameters.3. Parameters referenced by a specific symbol have special meanings and purposes, and are referred to as Bash's special internal variable reference. Basic Parameter extension:Character $ will guide paramete

Interpreter pattern (interpreter pattern): Given a language, defines a representation of its grammar and defines an interpreter that uses that representation to interpret sentences in the language.Here is a demo of the Interpreter mode:1 #!/usr/bin/env python2 #-*-coding:utf-8-*-3 4 __author__='Andy'5 """6 Liar design

Bash variable types and bash Variables Local variable: it acts on the Current shell and is invalid for other shell processes other than the current shell and the Current shell Sub-processes. Assign a value to a local variable name='value' Value can be a string or a variable. The referenced variable uses $ {name}, $ name, or ''. Note: single quotes are strongly referenced, while double quotes are weak refere