How can I create directory tree in C++/Linux?

Question

I want an easy way to create multiple directories in C++/Linux.

For example I want to save a file lola.file in the directory:

/tmp/a/b/c

but if the directories are not there I want them to be created automagically. A working example would be perfect.

Answer 1

system("mkdir -p /tmp/a/b/c")

is the shortest way i can think of.

It's not cross-platform but will work under Linux.

Answer 2

mkdir -p /dir/to/the/file

touch /dir/to/the/file/thefile.ending

Answer 3

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

int status;
...
status = mkdir("/tmp/a/b/c", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);

From here. You may have to do separate mkdirs for /tmp, /tmp/a, /tmp/a/b/ and then /tmp/a/b/c because there isn't an equivalent of the -p flag in the C api. Be sure and ignore the EEXISTS errno while you're doing the upper level ones.

Answer 4

The others got you the right answer, but I thought I'd demonstrate another neat thing you can do:

mkdir -p /tmp/a/{b,c}/d

Will create the following paths:

/tmp/a/b/d
/tmp/a/c/d

The braces allow you to create multiple directories at once on the same level of the hierarchy, whereas the -p option means "create parent directories as needed".

Answer 5

You said "C++" but everyone here seems to be thinking "Bash shell."

Check out the source code to gnu mkdir; then you can see how to implement the shell commands in C++.

Answer 6

Easy with boost.Filesystem : create_directories

create_directories("/tmp/a/b/c");

Answer 7

Here's a C function that can be compiled with C++ compilers.

/*
@(#)File:           $RCSfile: mkpath.c,v $
@(#)Version:        $Revision: 1.12 $
@(#)Last changed:   $Date: 2008/05/19 00:43:33 $
@(#)Purpose:        Create all directories in path
@(#)Author:         J Leffler
@(#)Copyright:      (C) JLSS 1990-91,1997-98,2001,2005,2008
@(#)Product:        :PRODUCT:
*/

/*TABSTOP=4*/

#include "jlss.h"
#include "emalloc.h"

#include <errno.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <string.h>
#include "sysstat.h"    /* Fix up for Windows - inc mode_t */

typedef struct stat Stat;

#ifndef lint
/* Prevent over-aggressive optimizers from eliminating ID string */
const char jlss_id_mkpath_c[] = "@(#)$Id: mkpath.c,v 1.12 2008/05/19 00:43:33 jleffler Exp $";
#endif /* lint */

static int do_mkdir(const char *path, mode_t mode)
{
    Stat            st;
    int             status = 0;

    if (stat(path, &st) != 0)
    {
        /* Directory does not exist */
        if (mkdir(path, mode) != 0)
            status = -1;
    }
    else if (!S_ISDIR(st.st_mode))
    {
        errno = ENOTDIR;
        status = -1;
    }

    return(status);
}

/**
** mkpath - ensure all directories in path exist
** Algorithm takes the pessimistic view and works top-down to ensure
** each directory in path exists, rather than optimistically creating
** the last element and working backwards.
*/
int mkpath(const char *path, mode_t mode)
{
    char           *pp;
    char           *sp;
    int             status;
    char           *copypath = STRDUP(path);

    status = 0;
    pp = copypath;
    while (status == 0 && (sp = strchr(pp, '/')) != 0)
    {
        if (sp != pp)
        {
            /* Neither root nor double slash in path */
            *sp = '\0';
            status = do_mkdir(copypath, mode);
            *sp = '/';
        }
        pp = sp + 1;
    }
    if (status == 0)
        status = do_mkdir(path, mode);
    FREE(copypath);
    return (status);
}

#ifdef TEST

#include <stdio.h>

int main(int argc, char **argv)
{
    int             i;

    for (i = 1; i < argc; i++)
    {
        if (mkpath(argv[i], 0777) == 0)
            printf("created: %s\n", argv[i]);
        else
            printf("failed to create: %s\n", argv[i]);
    }
    return(0);
}

#endif /* TEST */

The macros STRDUP() and FREE() are error-checking versions of strdup() and free(). The "sysstat.h" header can be replaced by <sys/stat.h>. And "jlss.h" declares mkpath().