Process Api Code

 

Operating system process API  code:

Article catalog

• Process API
• • Code1: RC = fork () the PID of the sub-process, when RC == 0, indicates the child process itself
  • Code2: The parent process uses wait () waiting to end the sub-process
  • Code3: EXEC () System Call - Make sub-process running with different processes of the parent process
  • Code4: Relocation output file

  • Process API

    Code1: RC = fork () the PID of the sub-process, when RC == 0, indicates the child process itself

    #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    
    int
    main(int argc, char *argv[])
    {
        printf("hello world (pid:%d)\n", (int) getpid());
        int rc = fork();
        if (rc < 0) {
            
            fprintf(stderr, "fork failed\n");
            exit(1);
        } else if (rc == 0) {
                    printf("hello, I am child (pid:%d)\n", (int) getpid());
        } else {
           
            printf("hello, I am parent of %d (pid:%d)\n",
    	       rc, (int) getpid());
        }
        return 0;
    }

  • Code2: The parent process uses wait () waiting to end the sub-process

    1. What is WAIT () do? : Once the process calls Wait, immediately block yourself, automatically analyze if WAIT is automatically analyzed that the current process has exited, if it finds such a sub-process that has become zombie, Wait will collect this sub-process information, And returned it completely; if you didn't find such a child process, Wait would have been blocked here until there is an emergence.
    2. return value: If you perform success, the sub-process identification code (PID) is returned if there is an error occurs. Failure caused in Errno.

  • #include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <sys/wait.h>
    
    int
    main(int argc, char *argv[])
    {
        printf("hello world (pid:%d)\n", (int) getpid());
        int rc = fork();
        if (rc < 0) {
            
            fprintf(stderr, "fork failed\n");
            exit(1);
        } else if (rc == 0) {
            
            printf("hello, I am child (pid:%d)\n", (int) getpid());
    	sleep(1);
        } else {
            
            int wc = wait(NULL);
            printf("hello, I am parent of %d (wc:%d) (pid:%d)\n",
    	       rc, wc, (int) getpid());
        }
        return 0;
    }
    

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