bash computer

Learning bash notes-input and output, bash hide output1. I/O redirection The I/O redirection is as follows: Cmd1 | cmd2: pipeline that receives the standard output of cmd1 as the standard input of cmd2. > File: redirects standard output to file. > File: redirects the standard output to file. If the file exists, it is appended > | File: Even if noclobber is set, the standard output is still fo

Bash Variable type:Environment variablesLocal variables (local variables)Positional variablesSpecial variablesLocal variables:Set Varname=value: scope for the entire bash process;Local variables:Local Varname=value: Scope is the current code snippet;Environment variable: The scope is the current shell process and its child processes, (the action variable itself uses VARNAME, the value of the action variable

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://

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

Bash basics man manual and bash basics manBash basics man Manual Penetration tests based on Android devices are implemented through various terminals. Therefore, it is particularly important to master Shell-related operations. Bash is a Unix Shell program written for GNU. This document selects the Kali Linux penetration test tutorial Based on Android devices. It

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

Bash: insufficient permissions and insufficient bash Permissions This problem occurs today when a file is opened on a terminal under ubuntu. Suddenly, the file is read-only, so you need to open its user permissions. The specific implementation is as follows: chmod 777/home/example/filename. In this way, all permissions of this file are opened and can be accessed as much as possible. The details of chmod are

Linux bash integrated instance bash Script Editor, linuxbash Note: This is a simple bash Script Editor, but it has been tested. The reason for writing this blog is to exercise loop control language, functions, location parameters, local variables, function parameter calls, and inter-function calls, there is also the parameters for Obtaining user options and optio

The operating environment of the Bash Shell:Configuration values are divided into the overall system configuration values and preferences of each person, only some files placed in different places! Path and command search orderWhen a command (such as LS) is released, which LS is it running? Run the command in a relative/absolute path, such as "/bin/ls" or "./ls"; Run by alias to find the command; Run by

 Today burst a bash rce loophole, powerful. Look at the analysis of foreigners, feel the need to write their own understanding of this loophole. First, the problem results from a command env. Prototype: env [OPTION] ... [Name=value] ... [COMMAND [ARGS] ...] That's what man says: Display, set, or remove environment variables,run a command in a modified environment. My understanding is that using the key=value of the ENV command will first change th

In fact, after editing the bash script, you can use the Bash-n-X two options for script checking, not necessarily to run the program when the need to modify the script.Bash not only has the meaning of running scripts.No news is good news.I'm going to modify the original script a little bit.The-n effect I can not demonstrate now, before it is possible to directly point out the syntax errorThis is the effect

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

In the process of reading any questions, welcome to communicate togetherEmail:[email protected]qq:1494713801when executing a script full_build.sh, I was always prompted :-bash:./full_build.sh:/bin/bash^m:bad interpreter:no such file or directoryOr remind syntax error:unexpected end of FileOne of the reasons for the above error is that the script file is in DOS format, that is, the line end of each line is i

Bash script exercises and bash scripts Exercise 1: 1. Add five users, user1,..., user5; 2. The password of each user is the same as the user name. After the password is added, the command execution result is not displayed; 3. After each user is added, it must be displayed that the user has been added successfully. Useradd user1 Echo "user1" | passwd -- stdin user1 >/dev/null Echo "User1 added ." C

Bash metacharacters (upper) and bash characters Metacharacters Function Example Carriage return line feed End a command Space Split elements in a command line Ls/etc Tab Command auto-completion # Start a line of comment # This is a comment line " Multiple characters referenced but allowed to be replaced "$ File". ba

Bash internal variable, Bash variable Bash internal variables Some internal commands are invisible in the directory list. They are provided by the Shell itself. Common internal Commands include echo, eval, execexport, readonly, read, shift, wait, exit and point (.) Echo variable table Display the specified variable in the variable table to the standard output. Ev

Bash remote code execution vulnerabilities are really much more powerful than heart drops, but the impact is not very broad, but yesterday's analysis of the article bash The Remote Code execution vulnerability analysis at the end of this paper mentions the bulk problem of the vulnerability. One of the easiest ways to do this is to use the search engine's hacking technology, where I use the Google hacking sy

Advanced Bash script, classic usage and cases, advanced bashIn linux, Bash scripts are very basic knowledge. You may feel very high when you listen to the scripts. Just like starting from the beginning, you may feel that script writing is a great tool. Although complicated scripts are very easy to understand, when we master the usage and skills of these scripts and practice more, we will always become a han