(done) 关于 GNU/Linux API setenv 的实验

写一个下面的代码来验证

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>int main() {// 设置环境变量 MY_VAR 的值为 "hello_world"if (setenv("MY_VAR", "hello_world", 1) != 0) {perror("setenv");return 1;}pid_t pid;// 使用 fork() 创建一个新进程pid = fork();if (pid < 0) {// 错误处理：fork() 返回负值表示创建子进程失败fprintf(stderr, "Fork failed\n");return 1;} else if (pid == 0) {// 在子进程中执行的代码printf("Child process: Hello, I am the child process! PID: %d\n", getpid());// 获取并打印设置的环境变量 MY_VAR 的值char *value = getenv("MY_VAR");if (value != NULL) {printf("in child, MY_VAR is set to: %s\n", value);} else {printf("MY_VAR is not set.\n");}pid_t pid;// 使用 fork() 创建一个新进程pid = fork();if (pid == 0) {char *value = getenv("MY_VAR");if (value != NULL) {printf("in grandchild, MY_VAR is set to: %s\n", value);} else {printf("MY_VAR is not set.\n");}}} else {// 在父进程中执行的代码printf("Parent process: Hello, I am the parent process! PID: %d\n", getpid());printf("Parent process: Child's PID: %d\n", pid);}// 父子进程都会执行的代码printf("Hello from process PID: %d\n", getpid());return 0;
}

编译并执行后，执行结果如下：

Parent process: Hello, I am the parent process! PID: 923571
Parent process: Child's PID: 923572
Hello from process PID: 923571
Child process: Hello, I am the child process! PID: 923572
in child, MY_VAR is set to: hello_world
Hello from process PID: 923572
in grandchild, MY_VAR is set to: hello_world
Hello from process PID: 923573

可以看到环境变量 MY_VAR 被传递给了儿子和孙子

此时我们在 terminal echo $MY_VAR 试试
在这里插入图片描述