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# Global variables
The global variables **will be** inherited by **child processes**.
You can create a global variable for your current session doing:
```bash
export MYGLOBAL="hello world"
echo $MYGLOBAL #Prints: hello world
```
This variable will be accessible by your current sessions and its child processes.
You can **remove** a variable doing:
```bash
unset MYGLOBAL
```
# Local variables
The **local variables** can only be **accessed** by the **current shell/script**.
```bash
LOCAL="my local"
echo $LOCAL
unset LOCAL
```
# List current variables
```bash
set
env
printenv
cat /proc/$$/environ
cat /proc/`python -c "import os; print(os.getppid())"`/environ
```
# Persistent Environment variables
### **Files that affect behavior of every user:**
* _**/etc/bash.bashrc**_: This file is read whenever an interactive shell is started (normal terminal) and all the commands specified in here are executed.
* _**/etc/profile and /etc/profile.d/\***_**:** This file is read every time a user logs in. Thus all the commands executed in here will execute only once at the time of user logging in.
* **Example: **
`/etc/profile.d/somescript.sh`
```bash
#!/bin/bash
TEST=$(cat /var/somefile)
export $TEST
```
### **Files that affect behavior for only a specific user:**
* _**\~/.bashrc**_: This file behaves the same way _/etc/bash.bashrc_ file works but it is executed only for a specific user. If you want to create an environment for yourself go ahead and modify or create this file in your home directory.
* _**\~/.profile, \~/.bash\_profile, \~/.bash\_login**_**:** These files are same as _/etc/profile_. The difference comes in the way it is executed. This file is executed only when a user in whose home directory this file exists, logs in.
**Extracted from:** [**here**](https://codeburst.io/linux-environment-variables-53cea0245dc9) **and** [**here**](https://www.gnu.org/software/bash/manual/html\_node/Bash-Startup-Files.html)
# Common variables
From: [https://geek-university.com/linux/common-environment-variables/](https://geek-university.com/linux/common-environment-variables/)
* **DISPLAY** β the display used by **X**. This variable is usually set to **:0.0**, which means the first display on the current computer.
* **EDITOR** β the userβs preferred text editor.
* **HISTFILESIZE** β the maximum number of lines contained in the history file.
* **HISTSIZE - **Number of lines added to the history file when the user finish his session
* **HOME** β your home directory.
* **HOSTNAME** β the hostname of the computer.
* **LANG** β your current language.
* **MAIL** β the location of the userβs mail spool. Usually **/var/spool/mail/USER**.
* **MANPATH** β the list of directories to search for manual pages.
* **OSTYPE** β the type of operating system.
* **PS1** β the default prompt in bash.
* **PATH - **stores the path of all the directories which holds binary files you want to execute just by specifying the name of the file and not by relative or absolute path.
* **PWD** β the current working directory.
* **SHELL** β the path to the current command shell (for example, **/bin/bash**).
* **TERM** β the current terminal type (for example, **xterm**).
* **TZ** β your time zone.
* **USER** β your current username.
# Interesting variables for hacking
## **HISTFILESIZE**
Change the **value of this variable to 0**, so when you **end your session** the **history file** (\~/.bash\_history) **will be deleted**.
```bash
export HISTFILESIZE=0
```
## **HISTSIZE**
Change the **value of this variable to 0**, so when you **end your session** any command will be added to the **history file** (\~/.bash\_history).
```bash
export HISTSIZE=0
```
## http\_proxy
The processes will use the **proxy** declared here to connect to internet through **http**.
```bash
export http_proxy="http://10.10.10.10:8080"
```
## https\_proxy
The processes will use the **proxy** declared here to connect to internet through **https**.
```bash
export https_proxy="http://10.10.10.10:8080"
```
## PS1
Change how your prompt looks.
**I have created **[**this one**](https://gist.github.com/carlospolop/43f7cd50f3deea972439af3222b68808) (based on another, read the code).
Root:
.png>)
Regular user:
.png>)
One, two and three backgrounded jobs:
.png>)
One background job, one stopped and last command didn't finish correctly:
.png>)
Support HackTricks and get benefits!
- Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
- Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
- Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
- **Join the** [**π¬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**π¦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
- **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**