export, unset

What it does

How to write it

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

Most used

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$ run as a normal user# run as root (or with sudo)

1. 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.

2. 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.

3. 3Keep a variable for every login

   $echo 'export EDITOR=vim' >> ~/.bashrc

   Tools like crontab -e, visudo and git use the EDITOR variable.

4. 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.

5. 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.

6. 6Remove a variable

   $unset http_proxy https_proxy

   Turns the proxy off for this shell again.

7. 7List the exported variables

   $export -p | head

   Same information as env, but in a form you could paste back into a shell.

8. 8Stop exporting a variable but keep it

   $export -n APP_ENV

   The value stays in this shell; new programs no longer get it.

9. 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.

10. 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.

11. 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.

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Files

~/.bashrc

Your exported variables for every shell.

/etc/profile.d/*.sh

Exported variables for all users.