env

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Without arguments, env prints all environment variables, one NAME=value per line. These are the variables that programs started from your shell receive.

With a command after it, env runs that command with extra, removed or no variables at all. The main shell does not change.

You also see env in the first line of scripts: #!/usr/bin/env python3 finds python3 through $PATH, so the script works on systems where the program is in another folder.

طريقة الكتابة

env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]

الخيارات 13

الأكثر استخدامًا

-i, --ignore-environment: Start with an empty environment (only the variables you give).
-u, --unset=name: Remove this variable from the environment of the command.
-C, --chdir=dir: Change to this folder before the command runs.
-S, --split-string=text: Split TEXT into separate arguments (used in shebang lines with options).
-0, --null: End each output line with a NUL byte instead of a new line.
-v, --debug: Print what env does, step by step.
--block-signal[=<sig>]: Block these signals for the command.
--default-signal[=<sig>]: Reset these signals to the default for the command.
--ignore-signal[=<sig>]: Make the command ignore these signals.
--list-signal-handling: Print the non-default signal handling to stderr.
-: Same as -i.
--help: Show help.
--version: Show the version.

أمثلة 11

$ مستخدم عادي# بصلاحية root (أو مع sudo)

1Show all environment variables
```
$env
```
Sorted output is easier to read: env | sort.
2Find one variable
```
$env | grep -i proxy
```
Shows HTTP_PROXY, https_proxy and others. Proxy variables often explain why curl or dnf fails.
3Run one command with an extra variable
```
$env LANG=C df -h
```
The command runs in English with standard formats. Good for scripts that read command output.
4Run a command without a variable
```
$env -u HTTP_PROXY -u HTTPS_PROXY curl -I https://intranet.example.com
```
Skip the proxy for one internal test without changing your shell.
5Run a program in a clean environment
```
$env -i PATH=/usr/bin:/bin HOME=/tmp bash -c 'env'
```
Shows what a program sees with almost no variables. Close to what cron and systemd give a job.
6Use env in the first line of a script
```
$head -1 deploy.py
#!/usr/bin/env python3
```
The script uses the first python3 in $PATH, for example from a virtual environment.
7Pass options to the interpreter in a shebang
```
$head -1 tool.sh
#!/usr/bin/env -S bash -euo pipefail
```
-S splits the text into several arguments. Without it, the line does not work on Linux.
8Compare the environment of root and your user
```
$env | sort > /tmp/me.txt; sudo env | sort > /tmp/root.txt; diff /tmp/me.txt /tmp/root.txt
```
sudo resets most variables. This shows what changes.
9Check the variables of a running process
```
#tr '\0' '\n' < /proc/$(pgrep -o sshd)/environ
```
Each process keeps the environment it started with. Good to debug a service.
10Run a command in another folder
```
$env -C /var/www/html ls -l
```
The shell stays in its own folder.
11Print variables safely for a script (NUL separated)
```
$env -0 | sort -z | tr '\0' '\n' | head
```
NUL separators are safe even when a value contains a new line.

انتبه

env shows only exported variables. A plain shell variable (X=1 without export) is not in the list; use set for all.
Secrets in environment variables can be read by root and by tools that dump the environment. Prefer files with tight permissions.
env NAME=value changes the variable only for that one command.

الملفات

/proc/PID/environ: The environment of a running process (NUL separated).
/etc/environment: Variables set for all users at login (simple NAME=value lines).

نصائح للحفظ

env = show, env NAME=val cmd = one command with a change, env -i = clean start.

`env`

ماذا يفعل

طريقة الكتابة

الخيارات 13

أمثلة 11

1Show all environment variables

2Find one variable

3Run one command with an extra variable

4Run a command without a variable

5Run a program in a clean environment

6Use env in the first line of a script

7Pass options to the interpreter in a shebang

8Compare the environment of root and your user

9Check the variables of a running process

10Run a command in another folder

11Print variables safely for a script (NUL separated)

انتبه

الملفات

نصائح للحفظ

الدليل الكامل

ماذا يفعل

طريقة الكتابة

الخيارات 13

أمثلة 11

1Show all environment variables

2Find one variable

3Run one command with an extra variable

4Run a command without a variable

5Run a program in a clean environment

6Use env in the first line of a script

7Pass options to the interpreter in a shebang

8Compare the environment of root and your user

9Check the variables of a running process

10Run a command in another folder

11Print variables safely for a script (NUL separated)

انتبه

الملفات

نصائح للحفظ

أوامر مرتبطة

مُستخدم في هذه الدروس

الدليل الكامل

`env`