Environment Variables
Overview
In this sample application, the POSIX setenv(), function is used to populate several environment
variables in C. Then, all environment variables are then printed.
If the user sets a new value for the ALERT environment variable, it is printed to standard
output, and then cleared via unsetenv().
Building and Running
This project outputs to the console. It can be built and executed on QEMU as follows:
west build -b qemu_riscv32 samples/posix/env
west build -t run
Sample Output
The program below shows sample output for a specific Zephyr build.
BOARD=qemu_riscv32
BUILD_VERSION=zephyr-v3.5.0-5372-g3a46f2d052c7
ALERT=
Setting Environment Variables
The shell command below shows how to create a new environment variable or update the value associated with an existing environment variable.
The C code that is part of this sample application displays the value associated with the
ALERT environment variable and then immediately unsets it.
uart:~$ posix env set ALERT="Happy Friday!"
uart:~$ ALERT="Happy Friday!"
uart:~$ posix env set HOME="127.0.0.1"
uart:~$
Getting Environment Variables
The shell command below may be used to display the value associated with one environment variable.
uart:~$ posix env get BOARD
qemu_riscv32
The shell command below may be used to display all environment variables and their associated values.
uart:~$ posix env get
BOARD=qemu_riscv32
BUILD_VERSION=zephyr-v3.5.0-5372-g3a46f2d052c7
ALERT=
Unsetting Environment Variables
The shell command below may be used to unset environment variables.
uart:~$ posix env unset BOARD