一、进程的创建（实例：读写鼠标键盘）
#include <stdio.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdlib.h> #include <string.h> int main(int argc, char const *argv[]) { pid_t pid; pid = fork(); if (pid < 0) { perror("fork error!"); exit(1); } if (pid > 0) { int fd = open("/dev/input/mouse0", O_RDWR); int cor = 0; while (1) { read(fd, &cor, sizeof(cor)); //sleep(1); printf("cor = %d\n", cor); } } if (pid == 0) { char buffer[1024]; while (1) { memset(buffer, 0, sizeof(buffer)); int n_r = read(0, buffer, sizeof(buffer) - 1); buffer[n_r] = '\0'; printf("buffer = %s\n", buffer); } } return 0; }
同一文件，进程的读写位置不同，读写位置不被共享
如果在创建进程前，打开文件，则读写位置被共享
二、exec函数族
在一个进程中调用里一个程序
调用之后，原文件下面的程序会被覆盖，不予执行
要以
NULL结尾
2.1 execl
int execl (const char *path, const char *arg, ..);
2.1.1 demo.c
demo
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[]) { for (size_t i = 0; i < argc; i++) { printf("argc[%ld] = %s\n", i, argv[i]); } pid_t pid = getpid(); pid_t ppid = getppid(); printf("pid = %d\n",pid); printf("ppid = %d\n",ppid); char buffer[1024]; int n_r = read(0, buffer, sizeof(1024) - 1); buffer[n_r] = '\0'; printf("buffer = %s\n", buffer); return 0; }
2.1.2 execl.c
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[]) { printf("hello world\n"); execl("./demo","./demo","xasxa","hahaha",NULL); printf("快乐暑假\n"); }
2.2 execv
int execv (const char *path, char *const argv[]);
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[]) { printf("hello world\n"); //execl("./demo","./demo","xasxa","hahaha",NULL); char *arg[] = {"./demo", "hello1", "hello2", NULL}; execv("./demo", arg); printf("快乐暑假\n"); }
2.3 execlp
int execIp (const char *file, const char *arg,...)
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[]) { printf("hello world\n"); //execl("./demo","./demo","xasxa","hahaha",NULL); //char *arg[] = {"./demo", "hello1", "hello2", NULL}; //execv("./demo", arg); execlp("/home/jsetc/2022.7c++/多进程/demo","./demo","world1","world2",NULL); printf("快乐暑假\n"); }
2.4 execvpe
int execvpe (const char *file, char *const argv[], char *const envp[);
env是环境变量
2.4.1 demo.c
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[], char **env) { for (size_t i = 0; i < argc; i++) { printf("argc[%ld] = %s\n", i, argv[i]); } for (size_t i = 0; i < argc; i++) { printf("env[%ld] = %s\n", i, env[i]); } pid_t pid = getpid(); pid_t ppid = getppid(); printf("pid = %d\n",pid); printf("ppid = %d\n",ppid); char buffer[1024]; int n_r = read(0, buffer, sizeof(1024) - 1); buffer[n_r] = '\0'; printf("buffer = %s\n", buffer); return 0; }
2.4.2 execvpe
#include <stdio.h> #include <sys/types.h> #include <unistd.h> int main(int argc, char const *argv[]) { printf("hello world\n"); //execl("./demo","./demo","xasxa","hahaha",NULL); char *arg[] = {"./demo", "hello1", "hello2", NULL}; char *env[] = {"UXAS = admin","PASSWD = 123","trytrytry",NULL}; //execv("./demo", arg); //execlp("/home/jsetc/2022.7c++/多进程/demo","./demo","world1","world2",NULL); execvpe("/home/jsetc/2022.7c++/多进程/demo", arg, env); printf("快乐暑假\n"); }
三、vfork、system
3.1 vfok
先执行子进程
如果没有exec，则会共享父进程资源，子进程一定要加exit(1)进行异常退出，不会造成二次释放
vfork比fork更节省空间
只有遇到exec的时候，才会开辟新空间
