四、进程操作

#include<stdio.h>
#include<fcntl.h>
#include<sys/uio.h>
#include<sys/stat.h>
#include<sys/types.h>
#include<unistd.h>
#include<string.h>
#include<sys/wait.h>
#include<stdlib.h>
int main(){
    pid_t chpid;
    int fd;
    char buf[50];
    int status;
    if((fd=open("temp", O_CREAT | O_RDWR | O_TRUNC, 0664)) == -1){
        perror("创建文件：");
        return 1;
    }
    if((chpid = fork() == 0)){
        puts("子进程正在运行\n");
        strcpy(buf, "子进程数据！");
        printf("子进程pid：%d\n", getpid());
        printf("父进程pid：%d\n", getppid());
        write(fd, buf, strlen(buf));
        close(fd);
        exit(0);
    }else{
        puts("父进程正在运行！\n");
        strcpy(buf, "父进程数据!");
        printf("子进程pid：%d\n", chpid);
        printf("父进程pid：%d\n", getpid());
        write(fd, buf, strlen(buf));
        close(fd);
    } 
    wait(&status);
    return 0;
}

#include<unistd.h>
#include<stdio.h>
extern char **environ;
int main(int argc, char* argv[]){
    puts("输出执行参数:\n");
    for(int i = 0; i < argc; i++){
        printf("参数%d:%s\n", i, argv[i]);
    }
    puts("输出环境变量:\n");
    for(int i = 0;environ[i] != NULL; i++){
        printf("%s\n", environ[i]);
    }
    return 0;
}

#include<unistd.h>
#include<stdio.h>
extern char **environ;
int main(int argc, char* argv[]){
    puts("first information\n");
    fflush(stdout);
    execve("beexec", argv, environ);
    puts("information two!");
    return 0;
}