使用system()执行命令时如何设置环境变量? [英] How to set an environment variable when using system() to execute a command?

问题描述

我正在Linux上编写C程序，需要使用system()执行命令，并且在执行该命令时需要设置环境变量，但是我不知道在使用<时如何设置env var. c0>.

I'm writing a C program on Linux and need to execute a command with system(), and need to set an environment variable when executing that command, but I don't know how to set the env var when using system().

推荐答案

如果要将环境变量传递给与父进程不同的子进程，则可以组合使用 setenv .假设您要将另一个PATH传递给您的孩子:

If you want to pass an environment variable to your child process that is different from the parent, you can use a combination of getenv and setenv. Say, you want to pass a different PATH to your child:

#include <stdlib.h>
#include <string.h>

int main() {
    char *oldenv = strdup(getenv("PATH")); // Make a copy of your PATH
    setenv("PATH", "hello", 1); // Overwrite it

    system("echo $PATH"); // Outputs "hello"

    setenv("PATH", oldenv, 1); // Restore old PATH
    free(oldenv); // Don't forget to free!

    system("echo $PATH"); // Outputs your actual PATH
}

否则，如果您只是创建一个新的环境变量，则可以使用 setenv 和 unsetenv ，如下所示:

Otherwise, if you're just creating a new environment variable, you can use a combination of setenv and unsetenv, like this:

int main() {
    setenv("SOMEVAR", "hello", 1); // Create environment variable
    system("echo $SOMEVAR"); // Outputs "hello"
    unsetenv("SOMEVAR"); // Clear that variable (optional)
}

当然不要忘了检查错误代码.

And don't forget to check for error codes, of course.

这篇关于使用system()执行命令时如何设置环境变量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！