The export command is used to set or export environment variables to take effect in the current shell and its child processes. 1. Use export VARIABLE_NAME=value to set environment variables, such as export PATH=/new/path:$PATH, you can temporarily add a path to the front of PATH; 2. To view exported variables, you can directly enter export or use declare -x to view detailed format; 3. To modify existing variables, such as export PS1="\\u@\h:\\w\\$ ", you can change the command prompt style, or temporarily change the program configuration path through export CONFIG_DIR=/tmp/config; 4. To use export in a script, you can share variables among multiple scripts, but the child process cannot modify the variable value of the parent process. It should be noted that the variables set by export are only valid for the current terminal session and are invalid after closing the terminal. When using it, you must avoid problems such as spelling, order errors or missing quotes.
The export
command is used in Linux and Unix systems to set or export environment variables to make them available to the current shell and its child processes. It is mainly used to temporarily modify the operating environment, such as setting paths, languages, debugging information, etc.
Set environment variables
The most common use of using export
is to set environment variables. The syntax is simple:
export VARIABLE_NAME=value
For example, if you want to temporarily add a path to PATH
, you can write it like this:
export PATH=/new/path:$PATH
The effect of this is to add /new/path
to the front of PATH
, and the system will prioritize searching for this path when looking for commands.
Note: The variables set in this way are only valid in the current terminal session and will be invalid after closing the terminal.
View exported variables
If you want to view the variables that have been exported with export
, you can directly enter:
export
Or add declare -x
to view the detailed format (commonly in script debugging):
declare -x
The output will look like this:
declare -x HOME="/home/user" declare -x PATH="/usr/local/bin:/usr/bin"
This helps you confirm that the current environment variable is set correctly.
Modify existing variables
Sometimes you need to modify an existing variable. For example, you want to set a clearer format for PS1
(command prompt):
export PS1="\u@\h:\w\$ "
This will allow the prompt to display the username, hostname and current directory, which facilitates the identification of the current location.
If you just want to temporarily change the function of a variable, such as debugging a program to use a different configuration path:
export CONFIG_DIR=/tmp/config
Then run your program and it will read the new configuration directory.
Use export in scripts
If you want certain variables to be shared among multiple scripts, you can use export
in the main script:
#!/bin/bash export MY_APP_ENV=production ./subscript.sh
As long as $MY_APP_ENV
is referenced in subscript.sh
, you can get this value.
However, it should be noted that the child process cannot in turn affect the variables of the parent process . That is to say, modifying MY_APP_ENV
in subscript.sh
will not affect the value in the main script.
Basically that's it. Using export
well will give you better control over the program running environment, especially when debugging, deploying, or switching configurations. Although it seems simple, it is easy to make mistakes if you are not careful, such as spelling errors, inverting the order, forgetting quotes, etc.
The above is the detailed content of How to use the `export` command. For more information, please follow other related articles on the PHP Chinese website!

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