[SOLVED] How to create directories using mkdir functio

robertjinx · 08-13-2011, 01:42 PM

Hello, how is it possible to create directories in C using function mkdir or system similar to command "mkdir -p"

in variable char dir I have the directory, but don't know how to call in using function system

system("mkdir -p",dir) // doesn't work

and function mkdir from C doesn't support "-p".

theNbomr · 08-13-2011, 02:36 PM

In C, the system() function takes only a single char pointer argument. If your compiler didn't warn you about this, then you should upgrade your C compiler, or upgrade the -W option. If it did warn you, then you probably should have heeded the warning. There is nothing to stop you from calling mkdir() in a loop, creating the chain of directories as the -p option of the commandline tool does. Just takes a little more code.

--- rod.

robertjinx · 08-13-2011, 02:38 PM

That doesnt help at all, I can't create the folder, they are created dynamically and to make sure which is which would modify the code way too much. I need something simple if possible, if not, then ok.

ta0kira · 08-13-2011, 02:40 PM

There is a mkdir (2) system call and C function you can use. You'd have to manually perform the -p operations yourself, maybe with a recursive function using mkdirat (2), basename (3), and dirname (3) (the C functions). For more info, type man [the number in ()] [name of the function], e.g. man 2 mkdir.
Kevin Barry

edit: This does the job using only C, if you're interested. It needs some more error checking, I'm sure.

Code:

#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <sys/stat.h>
#include <sys/types.h>


static int open_directory(char *nName, int pParent)
{
	int directory = -1;

	if (pParent == 0)
	directory = open(nName, O_RDONLY);

	else
	directory = openat(pParent, nName, O_RDONLY);

	if (directory < 0) return -1;

	struct stat info;
	if (fstat(directory, &info) != 0)
	{
	close(directory);
	return -1;
	}

	if (S_ISDIR(info.st_mode)) return directory;

	close(directory);
	return -1;
}


static int recursive_mkdir(char *pPath, mode_t mMode)
{
	if (strcmp(pPath, ".") == 0) return 0;
	if (strcmp(pPath, "/") == 0) return open("/", O_RDONLY);

	char *path_copy = strdup(pPath), *head = strdup(basename(pPath)),
	     *rest = strdup(dirname(path_copy));

	free(path_copy);

	int parent = recursive_mkdir(rest, mMode);

	if (parent < 0)
	{
	free(head);
	free(rest);
	return -1;
	}

	int directory = open_directory(head, parent);

	if (directory > 0)
	{
	free(head);
	free(rest);
	if (parent > 0) close(parent);
	return directory;
	}

	if (parent == 0)
	{
	if (mkdir(head, mMode) == 0) directory = open(head, O_RDONLY);
	else fprintf(stderr, "cannot create directory '%s': %s\n", head, strerror(errno));
	}

	else
	{
	if (mkdirat(parent, head, mMode) == 0) directory = openat(parent, head, O_RDONLY);
	else fprintf(stderr, "cannot create directory '%s': %s\n", head, strerror(errno));
	}

	free(head);
	free(rest);
	if (parent > 0) close(parent);

	return directory;
}


int main(int argc, char *argv[])
{
	int I;
	for (I = 1; I < argc; I++)
	{
	char *name_copy = strdup(argv[I]);
	int directory = recursive_mkdir(name_copy, 0755);

	if (directory > 0)
	{
	fprintf(stderr, "directory '%s' created recursively\n", argv[I]);
	close(directory);
	}

	else
	fprintf(stderr, "directory '%s' NOT created\n", argv[I]);

	free(name_copy);
	}
}

theNbomr · 08-13-2011, 02:53 PM

Quote:

Originally Posted by robertjinx

they are created dynamically

Not sure what that means. In contrast to being created.... ?

Quote:

and to make sure which is which would modify the code way too much. I need something simple if possible

Then use the system() call method. You will have to compose the single string argument that it takes.
I haven't checked, but if mkdir is not a shell built-in, you could launch it with a fork() + exec() method, and that would save you the hassle of composing a single string argument, since there is probably an existing exec() family call that takes arguments in a method more compatible with your code.
Either way, it won't be fast, but its the kind of thing you aren't likely to be calling in a tight loop anyway.

--- rod.

Nylex · 08-13-2011, 03:27 PM

Quote:

Originally Posted by theNbomr

if mkdir is not a shell built-in

It's not a built-in, it's part of coreutils

.

robertjinx · 08-14-2011, 04:20 AM

Ok guys, thank you. This helps to clear some stuff, but still doesn't help me

robertjinx · 08-14-2011, 06:00 AM

@ta0kira: now I realized the coolness in your small code, thx!