realpath

realpath.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>   

/* cc -Wall -Wextra -pedantic -Werror -o realpath realpath.c */
/* or */
/* gcc -std=gnu99 -Wall -Wextra -pedantic -Werror -o realpath realpath.c */

int usage (char * path, int rv) {
    printf("%s <path> returns the canonical pathname for <path>, which must exist\n", basename(path));
    return(rv);
}

int main(int argc, char **argv) {
  if (argc < 2) {
    exit(usage(argv[0], 1));
  }
  
  char *p = realpath(argv[1], NULL);
  if (p == NULL) {
    exit(usage(argv[0], 1));
  }
  
  printf("%s\n", p);
  return 0;
}