Shell builtins · bash builtin

`export`

Mark shell variables (or bash functions) to be passed to every program the shell starts.

export [-fn] [NAME[=VALUE] ...]    or    export -p

9 of 9 examples run in Debian 13.7 on 2026-10-31 · manual: bash(1), SHELL BUILTIN COMMANDS

A shell variable exists only inside the shell that set it. export NAME puts it into the environment, the list of NAME=value strings that is copied into every child process: programs, scripts and subshells started from then on. That is how PATH, HOME, EDITOR or an API_TOKEN reach the programs that read them.

The copy goes one way, downward. A child can change its copy, but nothing it does reaches the parent, which is why a script cannot set a variable in your terminal (unless you source it). And export affects children started after it; a program already running keeps the environment it was born with.

To give a variable to one command only, skip export and prefix the command: LANG=C sort file. To remove a variable from the environment but keep it in the shell, use export -n; to remove it entirely, unset. export -p (or plain export) lists what is exported.

Examples

Make a variable visible to child processes

$ COLOR=blue
> bash -c 'echo "child sees COLOR=[$COLOR]"'
> export COLOR
> bash -c 'echo "child sees COLOR=[$COLOR]"'

output

child sees COLOR=[]
child sees COLOR=[blue]

Before export, COLOR is a plain shell variable and the child bash gets nothing. After it, the variable is part of the environment of every command started later.

Set and export in one step

$ export API_URL=http://localhost:8080 RETRIES=3
> env | grep -E '^(API_URL|RETRIES)='

output

API_URL=http://localhost:8080
RETRIES=3

export NAME=value assigns and exports at once, for as many names as you list. env, being a separate program, shows what children receive.

Set a variable for a single command

$ TZ=Asia/Tokyo date +%H:%M-%Z
> date +%H:%M-%Z
> echo "TZ in this shell: [${TZ-unset}]"

output

05:19-JST
20:19-UTC
TZ in this shell: [UTC]

A NAME=value prefix puts the variable in that one command's environment only. date reads TZ from its environment; afterward the shell still has its own value (UTC in this sandbox), untouched.

A child cannot change the parent's variable

$ export STAGE=dev
> bash -c 'STAGE=prod; echo "child changed it to $STAGE"'
> echo "parent still has $STAGE"

output

child changed it to prod
parent still has dev

The child receives a copy of the environment. Its assignment changes only that copy, so the parent's value is untouched. Pass results back through output instead: STAGE=$(cmd).

List exported variables

$ export -p | grep -E 'HOME|EDITOR|LANG'

explain

output

declare -x EDITOR="vi"
declare -x HOME="/home/dev"
declare -x LANG="C.UTF-8"

export -p prints each exported variable as a declare -x command that could recreate it. Variables the shell inherited, such as HOME and LANG, are exported automatically; EDITOR comes from the environment this sandbox starts with.

Stop exporting a variable with -n

$ export TOKEN=abc123
> export -n TOKEN
> echo "shell still has: $TOKEN"
> bash -c 'echo "child sees: [$TOKEN]"'

output

shell still has: abc123
child sees: []

export -n removes the export flag but keeps the value in the current shell. Useful for keeping a secret away from the commands you run next.

Add a directory to PATH

$ mkdir -p ~/bin
> printf '#!/bin/sh\necho "hello from ~/bin"\n' > ~/bin/hello
> chmod +x ~/bin/hello
> export PATH="$HOME/bin:$PATH"
> hello
> echo "$PATH" | tr : '\n' | head -n 3

output

hello from ~/bin
/home/dev/bin
/usr/local/bin
/usr/bin

PATH is already exported, so reassigning it is enough, but writing export makes the intent clear. Prepending gives your directory priority. In a startup file this line belongs in ~/.profile or ~/.bashrc.

Export a function to child bash processes with -f

$ greet() { echo "hello, $1"; }
> export -f greet
> bash -c 'greet child'
> printf '%s\n' a b | xargs -n 1 bash -c 'greet "$1"' _

output

hello, child
hello, a
hello, b

export -f passes a function through the environment to child bash processes. This is how to call a shell function from xargs, find -exec or parallel, which can only start programs. Each value is passed as $1 (after a placeholder $0) rather than pasted into the code, so odd file names cannot inject commands. Other shells such as dash will not see exported functions.

Subshells see unexported variables, programs do not

$ LOCAL_ONLY=yes
> ( echo "subshell: $LOCAL_ONLY" )
> echo "pipe: $(echo "$LOCAL_ONLY")"
> bash -c 'echo "new bash: [$LOCAL_ONLY]"'

output

subshell: yes
pipe: yes
new bash: []

( ... ) and $( ... ) are forks of the current shell, so they inherit every variable. bash -c is a new program and gets only the environment. This difference is why a variable "works in the script but not in the program it runs".

Common pitfalls

Expecting a script to export a variable into your terminal. Children cannot change their parent; source the script instead.
export VAR=$(cmd) returns the status of export, which is 0, so a failing cmd goes unnoticed by set -e or &&. Assign first, then export VAR.
Spaces around =: export NAME = value exports three names. Write NAME=value with no spaces.
Exporting secrets more widely than needed: every program you start afterward can read them, including from /proc/PID/environ. Prefer a per-command prefix.

GNU vs BSD and macOS

The examples above ran the GNU/Linux version. These are the differences that matter on macOS and the BSDs (written from their documentation, not run here).

export NAME=value and export -p are POSIX. export -n and export -f are bash-only; in dash they are errors. zsh supports export with the same basic syntax.

Options worth knowing

A selection, described in our own words. For the full list, see bash(1), SHELL BUILTIN COMMANDS.

Option	What it does
`-p`	List all exported variables as reusable declare -x commands.
`-n`	Remove the export flag from the named variables, keeping their values.
`-f`	Treat the names as shell functions and export those (bash only).

Examples

Common pitfalls

GNU vs BSD and macOS

Options worth knowing

Related