How to implement the Unix comand "dirname"?

Question

I have no idea how to make the code for this command.

I had something but is not working. I think is a problem at the exec.

Can someone make it work?

i'm a newbie in this field.

#include<sys/stat.h>
#include<libgen.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<dirent.h>
#include<stdio.h>

void showArgs(int argc, char *argv[]){
    int i;
    for (i=0;i<argc;i++) {
        printf("Argument is %s ",argv[i]);
    }
}

int main(int argc, char*argv[])
{
int isdir(const char *path) {
   struct stat statbuf;
   if (stat(path, &statbuf) != 0)
       return 0;
   return S_ISDIR(statbuf.st_mode);
}
printf("Program started... \n");
showArgs(argc, argv);
if(argc == 2)
{
    if(isdir(argv[1]))
    {
        printf("Calling dir with parameter\n");
        execl("dirname",argv[1],NULL);
    }else{
        printf("invalid dir name\n");
}
}
return 0;
}

Answer 1

you're missing an argument to execl(). It should be:

execl("/usr/bin/dirname", "dirname", argv[1], (char*)NULL);

The first argument is the path to the command to execute, then the remaining arguments are the elements of the argv array. And argv[0] is the name of the command.

You can also use execlp(), which searches for the command using the PATH environment variable. Then the first argument can just be "dirname". But you still need to repeat it in argv[0].

Also, functions should not be defined inside other functions in C. The isdir() definition should be before main(), not inside it.