Creating a new directory in C - c

Question

I want to write a program that checks for the existence of a directory; if that directory does not exist then it creates the directory and a log file inside of it, but if the directory already exists, then it just creates a new log file in that folder.
How would I do this in C with Linux?

Answer 1

Look at stat for checking if the directory exists,
And mkdir, to create a directory.
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
struct stat st = {0};
if (stat("/some/directory", &st) == -1) {
mkdir("/some/directory", 0700);
}
You can see the manual of these functions with the man 2 stat and man 2 mkdir commands.

Answer 2

You can use mkdir:
$ man 2 mkdir
#include <sys/stat.h>
#include <sys/types.h>
int result = mkdir("/home/me/test.txt", 0777);

Answer 3

I want to write a program that (...) creates the directory and a (...) file inside of it
because this is a very common question, here is the code to create multiple levels of directories and than call fopen. I'm using a gnu extension to print the error message with printf.
void rek_mkdir(char *path) {
char *sep = strrchr(path, '/');
if(sep != NULL) {
*sep = 0;
rek_mkdir(path);
*sep = '/';
}
if(mkdir(path, 0777) && errno != EEXIST)
printf("error while trying to create '%s'\n%m\n", path);
}
FILE *fopen_mkdir(char *path, char *mode) {
char *sep = strrchr(path, '/');
if(sep) {
char *path0 = strdup(path);
path0[ sep - path ] = 0;
rek_mkdir(path0);
free(path0);
}
return fopen(path,mode);
}

Answer 4

int mkdir (const char *filename, mode_t mode)
#include <sys/types.h>
#include <errno.h>
#include <string.h>
if (mkdir("/some/directory", S_IRWXU | S_IRWXG | S_IRWXO) == -1) {
printf("Error: %s\n", strerror(errno));
}
For best practice it is recommended to use an integer-alias for mode. The argument mode specifies the file permissions for the new directory.
Read + Write + Execute: S_IRWXU (User), S_IRWXG (Group), S_IRWXO (Others)
Source:
https://www.gnu.org/software/libc/manual/html_node/Permission-Bits.html
If you want to know that the directory exists, lookup the errno's for EEXIST.