LINUX----进程替换,exec族函数

execl族函数的作用

exel族函数用于调用一个已经存在的可执行程序,将该程序的运行需要的代码区和数据区的数据覆盖原进程,这样就可以实现在一个进程中调度另一个进程.

简单实现一个小功能来看一看

mytest.c

#include <stdio.h>
#include <unistd.h>int main(){printf("I am mytest.c , pid = %d, ppid = %d\n",getpid(),getppid());execl("/home/lxs/c/execl/text.py","./text.py",NULL);printf("error\n");return 0;
}

text.py

print("I am Python!!")

执行结果(用c 语言调用了一个python程序)

exec族函数详解

一共六个函数,函数的前四个字母都为exec.

#include <unistd.h>
int execl(const char *pathname, const char *arg, .../* (char  *) NULL */);
int execlp(const char *file, const char *arg, .../* (char  *) NULL */);
int execle(const char *pathname, const char *arg, .../*, (char *) NULL, char *const envp[] */);
int execv(const char *pathname, char *const argv[]);
int execvp(const char *file, char *const argv[]);
int execvpe(const char *file, char *const argv[],char *const envp[]);

这些函数的命名规则:

l(list) 代表以列表的形式传参

v(vector)代表以数组的形式进行传参

p(path) 代表自主搜索环境变量,不需要传路径

e(ebv) 代表自主维护环境变量

调用六个函数

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <sys/types.h>
void Child1(){printf("I am child1, I show execl\n");execl("/usr/bin/ls","ls","-a","-l","--color",NULL);exit(1);
}
void Child2(){printf("I am child2, I show execv\n");char* const argv[] = {"ls","-a","-l","--color",NULL};execv("/usr/bin/ls",argv);exit(1);
}
void Child3(){printf("I am child3, I show execlp\n");execlp("ls","ls","-a","-l","--color",NULL);exit(1);
}
void Child4(){printf("I am child4, I show execvp\n");char* const argv[] = {"ls","-a","-l","--color",NULL};execvp("ls",argv);exit(1);
}
void Child5(){printf("I am child5, I show execle\n");char* const envp[] = {"HAHA = 1111111","HEHE = 2222222",NULL };execle("/home/lxs/c/execl/test","test",NULL,envp);exit(1);
}
void Child6(){printf("I am child6, I show execvpe\n");char* const argv[] = {"test",NULL};char* const envp[] = {"HAHA = 1111111","HEHE = 2222222",NULL };execvpe("./test",argv,envp);exit(1);
}int main(){pid_t num[10];num[1] = fork();if(num[1] == 0){Child1();}sleep(1);num[2] = fork();if(num[2] == 0){Child2();}sleep(1);num[3] = fork();if(num[3] == 0){Child3();}sleep(1);num[4] = fork();if(num[4] == 0){Child4();}sleep(1);num[5] = fork();if(num[5] == 0){Child5();}sleep(1);num[6] = fork();if(num[6] == 0){Child6();}sleep(1);int stat = 0;for(int i = 1;i<=6;i++){pid_t rid = waitpid(num[i],&stat,0);if(rid > 0){printf("wait child%d sucess,childexit code:%d\n",i,WEXITSTATUS(stat));}}
}