export

Set the export attribute for shell variables or functions.

Synopsis

export [-fn] [name[=word]]...
export -p

Description

Define one or more variables and set the export attribute.
Modify the value of one or more variables and set the export attribute.
Remove the export attribute from one or more variables.
Display all variables that have the export attribute.
Add the export attribute to one or more defined functions.
Remove the export attribute from one or more functions.
Display all functions that have the export attribute.

Options

-f: Refers to functions.
-n: Remove the export attribute from variables.
-p: Display all variables with the export attribute.
-pf: Display all functions with the export attribute.
-nf: Remove the export attribute from functions.
--: Subsequent options are ignored.

Parameters

name (optional): Variable name or defined function name.

value (optional): The value of the variable.

Return Value

export returns true unless an invalid option or name is provided.

Examples

# Display all exported variables
# export -p
# export
# Display all exported functions
# export -pf

# Delete demo variables first
# unset a b
# Define variables and export them
export a b=3
# Or define first and export later
b=3
export b

# Modify values of exported variables
export a=5 b=7
# Or assign values directly
a=5; b=7

# Remove export attribute from variables
export -n a b

# Delete demo functions first
unset func_1 func_2
# Create functions
function func_1(){ echo '123'; }
function func_2(){ echo '890'; }

# Export defined functions
export -f func_1 func_2

# Remove export attribute from functions
export -fn func_1 func_2

# Add environment variable (JAVA) to `~/.bashrc`
export PATH=/usr/local/jdk1.7.0/bin:$PATH
# Add current path to dynamic library path
export LD_LIBRARY_PATH=$(pwd):${LD_LIBRARY_PATH}

Common Errors

Adding the export attribute to an undefined function.
Removing the export attribute from a function/variable that is not exported.
Using options after --.

Q&A

Q: What is the purpose of setting the export attribute for variables or functions?

A: They become environment variables that can be accessed by child processes spawned by the current shell.

Q: If my script modifies an existing environment variable, will it take effect in the current terminal? Will it affect previously or subsequently opened terminals?

A: Only scripts executed via the source (or .) command will affect the current shell. Otherwise, the script runs in a sub-shell and its changes are lost when it exits. Previously opened terminals are not affected. Subsequently opened terminals are only affected if you modified a startup script like ~/.bashrc.

Q: I have a script that calls functions and variables defined in `~/.bashrc`. Why can't I use them when I run the script via `sh` or as an executable?

A: Ensure that you have exported them in ~/.bashrc.

Q: Can arrays and associative arrays be exported?

A: Yes (if your bash version supports them), but there are some known issues and limitations.

Q: Why does the output start with `declare` when I view exported attributes?

A: Because declare can also set export attributes for variables or functions. See the declare command for details.

Note

This is a bash built-in command. For more help, use the help command.

Knowledge Points

In info bash or the Bash Online Manual, section 3.7.3 (Shell Execution Environment) mentions:

shell parameters that are set by variable assignment or with set or inherited from the shell’s parent in the environment

shell functions defined during execution or inherited from the shell’s parent in the environment

A variable is a parameter denoted by a name. Sub-shells inherit exported variables and functions from the parent shell.

[root@localhost ~]# export
declare -x G_BROKEN_FILENAMES="1"
declare -x HISTSIZE="1000"
declare -x HOME="/root"
declare -x hostname="localhost"
declare -x INPUTRC="/etc/inputrc"
declare -x LANG="en_US.UTF-8"
declare -x LESSOPEN="|/usr/bin/lesspipe.sh %s"
declare -x logname="root"
declare -x LS_COLORS="no=00:fi=00:di=01;34:ln=01;36:pi=40;33:so=01;35:bd=40;33;01:cd=40;33;01:or=01;05;37;41:mi=01;05;37;41:ex=01;32:*.cmd=01;32:*.exe=01;32:*.com=01;32:*.btm=01;32:*.bat=01;32:*.sh=01;32:*.csh=01;32:*.tar=01;31:*.tgz=01;31:*.arj=01;31:*.taz=01;31:*.lzh=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.gz=01;31:*.bz2=01;31:*.bz=01;31:*.tz=01;31:*.rpm=01;31:*.cpio=01;31:*.jpg=01;35:*.gif=01;35:*.bmp=01;35:*.xbm=01;35:*.xpm=01;35:*.png=01;35:*.tif=01;35:"
declare -x mail="/var/spool/mail/root"
declare -x OLDPWD
declare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
declare -x pwd="/root"
declare -x SHELL="/bin/bash"
declare -x SHLVL="1"
declare -x SSH_CLIENT="192.168.2.111 2705 22"
declare -x SSH_CONNECTION="192.168.2.111 2705 192.168.2.2 22"
declare -x SSH_TTY="/dev/pts/0"
declare -x TERM="linux"
declare -x USER="root"