Linux下进程控制实验

 （1）fork（）创建子进程

 

#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <math.h>

/* 进程创建 */
void main(void)
{
    pid_t child;
    int status;

    printf("This will demostrate how to get child status\n");

    /* 创建子进程 */
    if((child=fork())==-1)
    {
        printf("Fork Error : %s\n", strerror(errno));
        exit(1);
    }
    else if(child==0) // 子进程
    {
        int i;
        printf("I am the child: %s\n", getpid());
        for(i=0;i<1000000;i++) sin(i);
        i=5;
        printf("I exit with %d\n", i);
        exit(i);
    }

    while(((child=wait(&status))==-1)&(errno==EINTR));  //子进程未结束

    if(child==-1)
        printf("Wait Error: %s\n", strerror(errno));
    else if(!status)             // 子进程退出值为0
        printf("Child %ld terminated normally return status is zero\n", child);
    else if(WIFEXITED(status))   // 子进程退出值0
        printf("Child %ld terminated normally return status is %d\n", child, WEXITSTATUS(status));
    else if(WIFSIGNALED(status)) // 子进程未获信号而退出
        printf("Chlid %ld terminated due to signal %d not caught\n", child, WTERMSIG(status));
}

(2）进程等待waitpid（）

 

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>

void die(const char *msg)
{
        perror(msg);
        exit(1);
}

void child2_do()
{
        printf("In child2: execute 'date'\n");

        sleep(5);
        if (execlp("date", "date", NULL) < 0) {
                perror("child2 execlp");
        }
}

void child1_do(pid_t child2, char *argv)
{
        pid_t pw;

        do {
                if (*argv == '1') {
                        pw = waitpid(child2, NULL, 0);
                }
                else {
                        pw = waitpid(child2, NULL, WNOHANG);
                }
                if (pw == 0) {
                        printf("In child1 process:\nThe child2 process has not exited!\n");
                        sleep(1);
                }
        }while (pw == 0);

        if (pw == child2) {
                printf("Get child2 %d.\n", pw);
                sleep(5);
                if (execlp("pwd", "pwd", NULL) < 0) {
                        perror("child1 execlp");
                }
        }
        else {
                printf("error occured!\n");
        }
}

void father_do(pid_t child1, char *argv)
{
        pid_t pw;

        do {
                if (*argv == '1') {
                        pw = waitpid(child1, NULL, 0);
                }
                else {
                        pw = waitpid(child1, NULL, WNOHANG);
                }

                if (pw == 0) {
                        printf("In father process:\nThe child1 process has not exited.\n");
                        sleep(1);
                }
        }while (pw == 0);

        if (pw == child1) {
                printf("Get child1 %d.\n", pw);
                if (execlp("ls", "ls", "-l", NULL) < 0) {
                        perror("father execlp");
                }
        }
        else {
                printf("error occured!\n");
        }
}

int main(int argc, char *argv[])
{
        pid_t child1, child2;

        if (argc < 3) {
                printf("Usage: waitpid [0 1] [0 1]\n");
                exit(1);
        }

        child1 = fork();

        if (child1 < 0) {
                die("child1 fork");
        }
        else if (child1 == 0) {
                child2 = fork();

                if (child2 < 0) {
                        die("child2 fork");
                }
                else if (child2 == 0) {
                        child2_do();
                }
                else {
                        child1_do(child2, argv[1]);
                }
        }
        else {
                father_do(child1, argv[2]);
        }

        return 0;
}

 

（3）结束进程函数 kill（）

 

#include <sys/wait.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>

int main( void )
{
    pid_t childpid;
    int status;
    int retval;

    childpid = fork();
    if ( -1 == childpid )
    {
        perror( "fork()" );
        exit( EXIT_FAILURE );
    }
    else if ( 0 == childpid )
    {
        puts( "In child process" );
        sleep( 100 );//让子进程睡眠，看看父进程的行为
        exit(EXIT_SUCCESS);
    }
    else
    {
        if ( 0 == (waitpid( childpid, &status, WNOHANG )))
        {
            retval = kill( childpid,SIGKILL );

            if ( retval )
            {
                puts( "kill failed." );
                perror( "kill" );
                waitpid( childpid, &status, 0 );
            }
            else
            {
                printf( "%d killed\n", childpid );
            }

        }
    }

    exit(EXIT_SUCCESS);
}