unix/linux进程详解——代码

#include <iostream>
#include <vector>
#include <cstdint>
#include <cstring>
#include <error.h>
#include <unistd.h>

using namespace std;

int main()
{
    //system("ps aux &");//run on background
    char *const ps_argv[]={"ps", "ax", 0};

//eg env
    char *const ps_envp[]={"PATH=/bin:/usr/bin","TERM=console",0};

//possible exec
    //execl("/bin/ps","ps","ax",0);//assume ps in the bin
    //execlp("ps","ps","ax",0);//assume /bin is in the PATH
    execle("/bin/ps","ps","ax",0,ps_envp);//pass own env

//execv("/bin/ps",ps_argv);
//    execvp("ps",ps_argv);
//    execve("/bin/ps",ps_argv,ps_envp);

//    execlp("ps","ps","ax",0);

pid_t new_pid;

new_pid = fork();
    new_pid = getpid();
    cout << new_pid << endl;
    switch (new_pid) {
    case -1:
        break;
    case 0:
        break;
    default:
        break;
    }
    cout << "errx" << endl;
    return 0;
}

#include <iostream>
#include <vector>

#include <cstdint>
#include <cstring>
#include <error.h>

#include <unistd.h>
#include <sys/types.h>

using namespace std;

int main()
{
    pid_t pid;
    string message;
    int n;

pid = fork();
    //pid = getpid();

//cout << pid << endl;

switch (pid) {
    case -1:
        perror("fork failed");
        exit(1);
    case 0:
        message = "this is the child";
        n=5;
        break;
    default:
        message = "this is the parent";
        n=3;
        break;
    }

for(; n > 0;n--)
    {
        cout<<message<<endl;
        sleep(1);
    }
    //cout << "errx" << endl;
    return 0;
}

this is the parent
this is the child
this is the parent
this is the child
this is the parent
this is the child
$ this is the child
this is the child

#include <iostream>
#include <vector>

#include <cstdint>
#include <cstring>
#include <error.h>

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

using namespace std;

int main()
{
    pid_t pid;
    string message;
    int n;
    int exit_code;

pid = fork();
    //pid = getpid();

//cout << pid << endl;

switch (pid) {
    case -1:
        perror("fork failed");
        exit(1);
    case 0:
        message = "this is the child";

n=5;
        exit_code = 37;//casual set
        break;
    default:
        message = "this is the parent";
        exit_code = 0;
        n=3;
        break;
    }

for(; n > 0;n--)
    {
        cout << message << ",which pid:" << getpid() << endl;

sleep(1);
    }

if(pid != 0)
    {
        int stat_val;
        pid_t child_pid;

child_pid = wait(&stat_val);

printf("child has finished: PID = %d\n",child_pid);
        if(WIFEXITED(stat_val))
            printf("child exited with code %d\n",WEXITSTATUS(stat_val));
        else {
            printf("child terminated abnormally\n");
        }
    }
    //cout << "errx" << endl;
    exit(exit_code);
}