export, unset

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A variable you set in Bash (NAME=value) is only known to that shell. export NAME puts it in the environment, so every program and script started from this shell gets a copy.

unset NAME removes a variable (or a function with unset -f).

To keep a variable for future logins, write the export line in ~/.bashrc (for you) or in a file in /etc/profile.d/ (for everybody).

طريقة الكتابة

export [-fn] [NAME[=VALUE] ...]
export -p
unset [-fv] NAME [NAME ...]

الخيارات 6

الأكثر استخدامًا

NAME=VALUE: Set the value and export it in one step.
-p: List all exported variables (as export lines).
-n: Remove the export mark: the variable stays in the shell but is no longer passed on.
-f: The names are shell functions (export a function to child shells).

unset

-v: The names are variables (the default).
-f: The names are functions.

أمثلة 11

$ مستخدم عادي# بصلاحية root (أو مع sudo)

1Set and export a variable in one step
```
$export APP_ENV=staging
$bash -c 'echo $APP_ENV'
staging
```
The new shell (a child program) sees the value.
2Add a folder to the PATH
```
$export PATH="$PATH:$HOME/bin"
```
Keep the old PATH and add your folder at the end. Put the line in ~/.bashrc to keep it.
3Keep a variable for every login
```
$echo 'export EDITOR=vim' >> ~/.bashrc
```
Tools like crontab -e, visudo and git use the EDITOR variable.
4Set a variable for all users
```
#echo 'export HISTTIMEFORMAT="%F %T "' > /etc/profile.d/history-time.sh
```
Every user gets times in history after the next login.

5Use a proxy for the tools in this shell

$export http_proxy=http://proxy.example.com:3128 https_proxy=http://proxy.example.com:3128

curl, dnf and pip read these variables.

6Remove a variable
```
$unset http_proxy https_proxy
```
Turns the proxy off for this shell again.
7List the exported variables
```
$export -p | head
```
Same information as env, but in a form you could paste back into a shell.
8Stop exporting a variable but keep it
```
$export -n APP_ENV
```
The value stays in this shell; new programs no longer get it.

9Export a function to a child script

$log() { echo "$(date +%T) $*"; }
$export -f log
$bash -c 'log "hello from child"'

Child Bash processes can use the function.

10Pass settings to a container or a tool without editing files
```
$export KUBECONFIG=$HOME/.kube/staging.yaml
$kubectl get nodes
```
One variable switches the cluster for this terminal only.
11Remove a secret from the shell after use
```
$export DB_PASSWORD='s3cret'; ./migrate.sh; unset DB_PASSWORD
```
Shorter life for the secret in the shell. Better: let the tool read it from a protected file.

انتبه

No spaces around =: export A = 1 is wrong.
A child can never change the variables of its parent. A script that exports a variable does not change your shell, unless you run it with source.
unset PATH breaks the shell until you set PATH again.

الملفات

~/.bashrc: Your exported variables for every shell.
/etc/profile.d/*.sh: Exported variables for all users.

نصائح للحفظ

Set: NAME=value. Pass on: export NAME. Both: export NAME=value. Remove: unset NAME.

`export, unset`

ماذا يفعل

طريقة الكتابة

الخيارات 6

unset

أمثلة 11

1Set and export a variable in one step

2Add a folder to the PATH

3Keep a variable for every login

4Set a variable for all users

5Use a proxy for the tools in this shell

6Remove a variable

7List the exported variables

8Stop exporting a variable but keep it

9Export a function to a child script

10Pass settings to a container or a tool without editing files

11Remove a secret from the shell after use

انتبه

الملفات

نصائح للحفظ

الدليل الكامل

ماذا يفعل

طريقة الكتابة

الخيارات 6

unset

أمثلة 11

1Set and export a variable in one step

2Add a folder to the PATH

3Keep a variable for every login

4Set a variable for all users

5Use a proxy for the tools in this shell

6Remove a variable

7List the exported variables

8Stop exporting a variable but keep it

9Export a function to a child script

10Pass settings to a container or a tool without editing files

11Remove a secret from the shell after use

انتبه

الملفات

نصائح للحفظ

أوامر مرتبطة

مُستخدم في هذه الدروس

الدليل الكامل

`export, unset`