Question

After opening a directory, I wanna check if a command (such as ls) resides within a given directory but open returns an integer i think.. after tokenization, I’m left with some directories… so what can i do?? I was told to use only open() function :((

int       Account_Master;
    .  .  .
  Account_Master = open ("accounts.dat", O_RDONLY);
  if (Account_Master >0) {
    printf ("Open succeeded.\n");

this is the example i used.. whats the point of opening a file if no use?

Answer 1

The integer returned can be given to other functions, such as read, fstat, and close. If you just want to check whether a file exists, use stat:

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
int main(int argc, char* argv[]) {
  struct stat statInfo;
  char* fn = argc>1 ? argv[1] : "/bin/ls";
  int res = stat(fn, &statInfo);
  if (res != 0) {
     printf("File %s does not exist.\n", fn);
     return 1;
  }
  if (statInfo.st_mode & S_IXUSR) {
     printf("Owner can execute the file %s\n", fn);
     return 0;
  }
  printf("File %s is there, but not executable.\n", fn);
  return 2;
}

If you don’t want to check a single file, but a whole directory, have a look at readdir instead.