linux应用编程之进程编程

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1 进程概念

在自身的虚拟空间中运行的占据系统资源的程序。

2 父子进程

fork一个进程以后，都将会产生一个子进程，这个子进程拷贝了父进程的资源(可以使用execve来覆盖父进程的运行代码)。

3 僵死进程

当子进程退出，而父进程并没有回收机制(收尸)或者显式的忽略该信号的话，子进程就将变成僵尸进程。

4 例子

1）

#include <stdio.h>#include <sys/types.h>#include <sys/wait.h>#include <unistd.h>#include <stdlib.h>int main(){pid_t chl_pid;int status;if((chl_pid = fork()) < 0){printf("fork error\n");exit(-1);}else if(chl_pid >0){/*if parent dones't process the signal or ignore this signal,*then child will be a zimble signal*(of course,there will be another method to kill the zimble *process,which is kill the parent process,then the child *process will be adoptted to 1st process)*/printf("this is parent\nchild pid : %d",chl_pid);wait(&status);while(1);}else{printf("this is child\n");}return 0;}

2）多个子进程

#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/types.h>#include <sys/wait.h>int main(){int ret;int wait_ch1_status,wait_ch2_status; //wait for child process's signalpid_t pid_1,pid_2;if( (ret =fork()) == 0 ){printf("child 1 process\n");exit(1);}else{pid_1 = ret;printf("pid 1 :%d\n",pid_1);//father if( (ret = fork()) ==0){printf("child 2 process\n");exit(1);}else{pid_2 = ret;printf("pid 2:%d\n",pid_2);printf("parent process\n");waitpid(pid_1,&wait_ch1_status,P_PID);waitpid(pid_2,&wait_ch2_status,P_PID);while(1);}}}

3) execve()

/* myecho.c  */#include <stdio.h>#include <stdlib.h>int main(void){printf("123\n");exit(0);}

/* execve.c */#include <stdio.h>#include <stdlib.h>#include <unistd.h>int main(int argc,char *argv[]){char *newargv[] = {"hello","world",NULL};char *env[] = {NULL};execve(argv[1],newargv,env);perror("execve");exit(EXIT_FAILURE);}

编译后

执行 $ ./execve ./myecho

打印123

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