Program using EXECLP() System Call

Ex. No.: 4(c)

Program using EXECLP() System Call

AIM:

               Write a C program using execlp system call  

execlp: This system call is used by one of the processes(parent or child) to replace the process’s memory space with a new memory image of the program containing the execlp system call and starts its execution.

Syntax:

int execlp(const char *file, const char *arg, ...);

          The functions execlp will duplicate the actions of the shell in searching for an executable file if the specified file name does not contain a slash (/) character. The search path is the path specified in the environment by the PATH variable. If this variable isn't specified, the default path ``:/bin:/usr/bin'' is used. In addition, certain errors are treated specially.

Return value

If any of the execlp functions returns, an error will have occurred. The return value is -1, and the global variable errno will be set to indicate the error. 

#include<stdlib.h>

#include<ctype.h>

#include<sys/types.h>

#include<unistd.h>

#include<stdio.h>

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

{

  pid_t child_pid;

  int choice;

  printf("\nOptions :\n1.Date\n2.ls\n3.File Type");

  printf("\n4.Word count\n5.Users\n6.Exit\n");

  printf("Enter ur choice :");

  scanf("%d",&choice);

  child_pid = fork();

  if (child_pid == 0)

   {

     printf("\nChild Process:\n");

     switch(choice)

     {

       case 1:

         printf("\n");

         execlp("date","date",NULL);

         break;

       case 2:

         printf("\n");

         execlp("ls","ls",NULL);

         break;

       case 3:

         printf("\n");

         execlp("file","file","hello",NULL);

         break;

       case 4:

         printf("\n");

         execlp("wc","wc","hello",NULL);

         break;

       case 5:

         printf("\n");

         execlp("who","who",NULL);

         break;

       default:

         break;

     }

     printf("\nChild process terminated:\n");

   }

  return 0;

}

Output :

[cs281016@linux]$cc execlp.c

[cs281016@linux]$ ./a.out execlp.c

Options :

1.Date

2.ls

3.File Type

4.Word count

5.Users

6.Exit

Enter ur choice :1

Child Process:

Tue Aug  9 01:24:37 IST 2005

Options :

1.Date

2.ls

3.File Type

4.Word count

5.Users

6.Exit

Enter ur choice :2

Child Process:

a.out  cp.c        execvp.c    forkk.c   pri.c    

bg     disp.c      execvp.out  fork.out  priority.c  

big    execlp.c    fibo        hello     round1.c  

count  execlp.out  fork.c      odd       round1.c  

Options :

1.Date

2.ls

3.File Type

4.Word count

5.Users

6.Exit

Enter ur choice :3

Child Process:

hello: ASCII text

Options :

1.Date

2.ls

3.File Type

4.Word count

5.Users

6.Exit

Enter ur choice :4

Child Process:

4       7      41 hello

Options :

1.Date

2.ls

3.File Type

4.Word count

5.Users

6.Exit

Enter ur choice :6

Child Process:

Child process terminated.

Result:

  Thus a C program is implemented using execlp system call.