Unix System Calls - fork, getpid, getppid

// System calls

// fork, exec, getpid, getppid, exit

#include<sys/types.h>   

#include<stdio.h>     

#include<unistd.h>

#include<sys/wait.h>

#include <stdlib.h>

int main()

{

    pid_t pid;

    

    /* fork a child process */

    pid = fork();

    

    if (pid < 0) 

        { 

            /* error occurred */

            fprintf(stderr, "Fork Failed");

            return 1;

    }

    else if (pid == 0) 

        {   

            /* child process */

            printf("\nExecuting in child process");

            printf("\n child process pid=%d ", getpid());

            printf("\n parent process pid=%d ", getppid());

            printf("\n Executing ls command.\n");

            execlp("/bin/ls","ls",NULL);

            exit(0);

    }

        else 

        { 

            /* parent process */

        /* parent will wait for the child to complete */

        printf("\nExecuting in parent process, pid=%d \n", getpid());

        wait(NULL);

        printf("Child Complete");

    }

    return 0;

}

Unix System Calls - wait exit exec

// Unix system calls

// exec, exit, wait

#include<stdio.h>

#include<string.h>

#include<sys/types.h>

#include<unistd.h>

int main(int argc, char *argv[])

{

          pid_t pid;

          int cstatus;            

          pid_t c;                

          pid=fork();

         

          if(pid == -1)

                   printf("\n Error in creating process ");

          else if(pid == 0)

          {

                   printf("\nExecuting in child process");

                   execvp(argv[1], &argv[1]);

                    perror("exec failure");

                   exit(1);

          }

          else

          {

                    printf("\nExecuting in parent process");

                    c = wait(&cstatus); /* Wait for child to complete. */

                   printf("\nParent: Child %ld exited with status = %d\n", (long) c, cstatus);

          }       

}

Unix System Calls - stat

Unix System Calls

// Unix system calls

// stat

#include <unistd.h>

#include <stdio.h>

#include <sys/stat.h>

#include <sys/types.h>

void main(int argc, char **argv)

{

    if(argc != 2)   

        printf("Usage error: Invalid number of arguments.");

    struct stat fs;

    if(stat(argv[1],&fs) < 0)   

        printf("Usage error: File / directory does not exist.");

    printf("Information for %s\n",argv[1]);

    printf("File Size: \t\t%d bytes\n",fs.st_size);

    printf("File inode: \t\t%d\n",fs.st_ino);

    printf("File mode: \t\t%d\n",fs.st_mode);

    printf("user ID of file owner: \t%d\n",fs.st_uid);

    printf("File last access time: \t%d\n",fs.st_atime);

    

}