Programming a shell..

First, this is a homework assignment.
I am to program a shell in C or C++. It has a variety of commands that I have working, but I am unsure about this one in particular.

This is from the assignment:

Now I am getting better at using Ubuntu, and I have looked up the more filter, but how do I use it in a programmatic way? Also, we are NOT to use the system() command.
The "user manual" is a readme text file.

Thanks!

 

I am starting to think I can run it through an exec() command. Here is what I have, but it is not working....

Code (Text):

1.  
2. void Help()
3. {
4.     pid_t pid;
5.    
6.     pid = fork();                               // create a new process
7.     if (pid < 0)
8.             cout << "Error creating child\n";
9.     else if (pid == 0)
10.     {
11.         char file[1024];
12.         getcwd(file,1024);
13.         strcat(file,"/readme");
14.  
15.         // child process
16.             if(execl("/usr/bin/more",file,(char* const*)NULL))
17.             {
18.                     cout << "Error associating process with program.\n";
19.                         _exit(-1);
20.             }
21.     }
22.     else // parent process
23.     {
24.  
25.         wait(NULL);  // wait for child process
26.     }
27. }
28.  

 

Ok, I managed to fix my problem, sort of.
I'll post my fix:

Code (Text):

1.  
2. void Help(char* readme)
3. {
4.     pid_t pid;
5.     pid = fork();
6.     if(pid == -1)
7.             cout << "Error Creating child\n";
8.     else if ( pid == 0)
9.     {
10.             char* arg[4];
11.             arg[0] = (char*)"/usr/bin/more";
12.             arg[1] = (char*)"-d";
13.             arg[2] = readme;
14.             arg[3] = NULL;
15.        
16.             if(execv(arg[0],arg))
17.             {
18.                     cout << "Error: Cannot open readme file\n";
19.                     _exit(-1);
20.             }
21.     }
22.     else if ( pid != 0)
23.     {
24.             wait(NULL);
25.             cout << endl;
26.     }
27. }
28.  

Now, the above code works on my Mac, but not under Ubuntu. It seems that either they moved the more filter somewhere else, or they just got rid of it in favor or the less filter.
If I replace:

Code (Text):

1.  
2. arg[0] = (char*)"/usr/bin/more";
3.  

with:

Code (Text):

1.  
2. arg[0] = (char*)"/usr/bin/less";
3.  

Then it works under Ubuntu and Mac.
Thanks for the suggestions, however, he wanted me to use the more filter, not recreate it.


EDIT: Fixed! I was looking in the wrong directory. more is in /bin not /usr/bin. Hope this helps someone in the future!