printenv

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طريقة الكتابة

printenv [OPTION]... [VARIABLE]...

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$ مستخدم عادي# بصلاحية root (أو مع sudo)

1. 1Print one value

   $printenv HOME
   /home/student

   Only the value, no name. Easy to use in scripts.

2. 2Print several values

   $printenv USER SHELL LANG
   student
   /bin/bash
   en_US.UTF-8

   One line per variable, in the order you asked.

3. 3Print all environment variables

   $printenv | sort

   Same list as env, sorted by name.

4. 4Check if a variable exists

   $printenv KUBECONFIG >/dev/null || echo "KUBECONFIG is not set"

   The exit code is 1 when the variable is missing.

5. 5Make a script stop when a needed variable is missing

   $for v in DB_HOST DB_USER; do printenv "$v" >/dev/null || { echo "missing $v"; exit 1; }; done

   Fail early with a clear message, before the script touches anything.

6. 6Check the proxy settings

   $printenv | grep -i _proxy

   Wrong proxy variables are a common reason why downloads fail on servers.

7. 7See the PATH one folder per line

   $printenv PATH | tr ':' '\n'

   Easy to see a wrong or missing folder.

8. 8Compare a variable as your user and with sudo

   $printenv PATH; sudo printenv PATH

   sudo uses its own safe PATH (from secure_path in sudoers).

9. 9Check what a systemd service gets (test a unit)

   $systemd-run --user --wait --pipe printenv | head

   Runs printenv the way a service would run, so you see its environment.

10. 10Print a variable that a CI job sets

    $printenv CI_COMMIT_SHA

    CI systems pass build data in environment variables; print them to debug a pipeline step.

11. 11Print values with NUL separators

    $printenv -0 USER HOME | xargs -0 -n1 echo

    Safe for values that contain spaces or new lines.

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