Programming Forums > Application Development > C++

Siren201 · Sep 19th, 2004, 8:32 AM

Hi

Just wondering if anyone know how to
a) Check if a directory exists
b) Create it if it does'nt

This is in unix using C

I tried creating the directory using
execlp("mkdir" , dirName)
but that did'nt work. Besides I actually need a way of checking if it exists first.

Cheers

Ashcroft · Sep 19th, 2004, 9:41 AM

You don't really have to do both those things seperately.

You can do the following

(Toggle Plain Text)

#include <sys/types.h>
#include <sys/stat.h>

const char *dir_name = "foo";
mode_t mode = 0755;
if (mkdir(dir_name, mode) == -1) {
  /* -1 on error, check errno for exact error */
  if (errno == EEXIST) {
   printf("directory already exists\n");
  }
}

If you have to check if a file exists as an operation seperate from creating it you can use stat.

(Toggle Plain Text)

#include <sys/types.h>
#include <sys/stat.h>

const char *dir_name = "foo";
struct stat sb;
if (stat(dir_name, &sb) == -1) {
  if (errno == ENOENT) {
   printf("directory does not exist\n");
  }
} else {
  /* verify that it is a directory, the name exists but it might be a regular file */
  if ((sb.st_mode & S_IFDIR) != S_IFDIR) {
   printf("%s exists but is not a directory\n", dir_name);
  }
}

If the directory does exist then sb will contain information about it., if you need to tell if a file is a directory or a regular file or has specific permissions. Check the stat man page and sys/stat.h for all the stuff you can tell about a file and what the possible values of errno mean.

Sep 19th, 2004, 9:41 AM	#2
Ashcroft Programmer Join Date: Sep 2004 Posts: 38 Rep Power: 0	You don't really have to do both those things seperately. You can do the following (Toggle Plain Text) #include <sys/types.h> #include <sys/stat.h> const char dir_name = "foo"; mode_t mode = 0755; if (mkdir(dir_name, mode) == -1) { / -1 on error, check errno for exact error / if (errno == EEXIST) { printf("directory already exists\n"); } } #include <sys/types.h> #include <sys/stat.h> const char dir_name = "foo"; mode_t mode = 0755; if (mkdir(dir_name, mode) == -1) { /* -1 on error, check errno for exact error / if (errno == EEXIST) { printf("directory already exists\n"); } } If you have to check if a file exists as an operation seperate from creating it you can use stat. (Toggle Plain Text) #include <sys/types.h> #include <sys/stat.h> const char dir_name = "foo"; struct stat sb; if (stat(dir_name, &sb) == -1) { if (errno == ENOENT) { printf("directory does not exist\n"); } } else { /* verify that it is a directory, the name exists but it might be a regular file / if ((sb.st_mode & S_IFDIR) != S_IFDIR) { printf("%s exists but is not a directory\n", dir_name); } } #include <sys/types.h> #include <sys/stat.h> const char dir_name = "foo"; struct stat sb; if (stat(dir_name, &sb) == -1) { if (errno == ENOENT) { printf("directory does not exist\n"); } } else { /* verify that it is a directory, the name exists but it might be a regular file */ if ((sb.st_mode & S_IFDIR) != S_IFDIR) { printf("%s exists but is not a directory\n", dir_name); } } If the directory does exist then sb will contain information about it., if you need to tell if a file is a directory or a regular file or has specific permissions. Check the stat man page and sys/stat.h for all the stuff you can tell about a file and what the possible values of errno mean.

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Sep 19th, 2004, 8:32 AM	#1
Siren201 Newbie Join Date: Sep 2004 Posts: 1 Rep Power: 0	Hi Just wondering if anyone know how to a) Check if a directory exists b) Create it if it does'nt This is in unix using C I tried creating the directory using execlp("mkdir" , dirName) but that did'nt work. Besides I actually need a way of checking if it exists first. Cheers

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