What does Linux export mean?

Linux export is a command used to set or display environment variables. Its syntax is "export [-fnp][variable name]=[variable setting value]". The parameter "-f" represents the function name. The parameter "-n" means to delete the specified variable, and the parameter "-p" means all the environment variables assigned to the program by the shell.

What does the Linux export command mean?

Linux export command

Function description: Set or display environment variables.

Syntax: export [-fnp][variable name]=[variable setting value]

Supplementary instructions: When executing a program in the shell, the shell will provide a set of environment variables. Export can add, modify or delete environment variables for use by subsequent programs. The export is only valid for this login operation.

Parameters:

-f represents the function name in [variable name].

-n Delete the specified variable. The variable is not actually deleted, it is just not output to the execution environment of subsequent instructions.

-p Lists all environment variables assigned to the program by the shell.

When a variable is created, it is not automatically known to shell processes created after it. The command export can pass the value of the variable to the subsequent shell. When a shell script is called and executed, it does not automatically gain access to variables defined in the original script (the caller) unless these variables have been explicitly made available. The export command can be used to pass the value of one or more variables to any subsequent script.

After logging in to the system, the system will start a user shell. In this shell, you can use shell commands or declare variables, and you can also create and run shell script programs. When running a shell script program, the system will create a subshell. At this time, there will be two shells in the system, one is the shell started by the system when logging in, and the other is the shell created by the system to run the script program. When a script program finishes running, its script shell will terminate and you can return to the shell before executing the script. In this sense, a user can have many shells, each of which is derived from some shell (called a parent shell).

Variables defined in a subshell are only valid within the subshell. If a variable is defined in a shell script, when the script is running, the defined variable is only a local variable within the script, and other shells cannot reference it. To make the value of a variable available in other If changed in the shell, you can use the export command to output the defined variables.

The export command will cause the system to define a copy of this variable when each new shell is created. This process is called variable output.

#echo $PKG_PATH The variables created at any time are only local variables of the current shell, so they cannot be used by other commands or shell programs run by the shell. export is to pass the environment variables you set to the sub-SHELL of the current SHELL so that they are valid in the sub-SHELL.

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