How to create a microshell in C/C++?

Question

I have an assignment to "Create a microshell in C/C++" and I am trying to figure out what exactly that means. I have this C code so far:

#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <sstream>
#include <stdlib.h>
#include <sys/utsname.h>

int main(void)
{

char buf[1024];
pid_t pid;
int status;
printf("%% ");

while (fgets(buf,1024,stdin) != NULL)
{

    buf[strlen(buf) -1] =0; //remove the last character. Important!

    if ((pid = fork()) <0)
            printf("fork error");
    else if (pid==0)
    {       /* child */
            execlp(buf, buf, (char *) 0);
            printf("couldn't execute: %s", buf);

            exit(127);
    }//else if end

    /* parent */
    if ( (pid = waitpid(pid, &status, 0)) <0)
            printf("waitpid error");

    printf("%% ");
}//while end

exit(0);
}//main end

I need to be able to invoke it using just it's name. So the name of my program is prgm4.cpp, so I need to be able to do this:

%>prgm4
prgm4>(user enters command here)

What do I need to add to my code to be able to do this? Also, how would I alter this to accept a command with two words, such as cat file.txt? Thank you for any assistance.

Answer 1

If I understand you correctly, you're just asking how to run your program with it's name, rather than with a full path to the file.

$ prgm4 # You want this...
$ /path/to/my/program/prgm4 # ...Instead of this.

If that's the case, it doesn't have anything to do with the program itself. You need to move your program to a place that's in the $PATH variable, like /usr/bin on Linux, or edit the PATH variable to include the directory it's already in. For example:

$ PATH="/path/to/my/program:$PATH"

See this Super User question for more details.