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 - open, read, write, close, exit

// Unix system calls

// open, read, write, close system calls

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h> 

#include <fcntl.h>    

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

{

        int fd;

        int n_char=0;

              char buffer[10];

        fd=open(argv[1],O_RDONLY);

        if (fd==-1)

        {

                   printf("File open error.");

                   exit(1);

        }

       

        while( (n_char=read(fd, buffer, 1))!=0)

                   n_char=write(1,buffer,n_char);

       

        close(fd)

        return 0;

}

Unix System Calls - opendir readdir

// Unix system calls

// opendir, readdir

#include <stdio.h>

#include <dirent.h>

int main()

{

          struct dirent *de; 

          DIR *dr = opendir(".");

          if (dr == NULL)

          {

                   printf("Could not open current directory" );

                   return 0;

          }

          while ((de = readdir(dr)) != NULL)

                             printf("%s\n", de->d_name);

          closedir(dr);

          return 1;

}

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);

    

}