library call for directory path creation?

[Ruben de Groot]

On Tue, Feb 01, 2005 at 04:39:21PM -0500, Louis LeBlanc typed:
> On 02/01/05 12:58 PM, Michael C. Shultz sat at the `puter and typed:
> > On Tuesday 01 February 2005 11:35 am, Louis LeBlanc wrote:
> > > I know there might be a better place for this question, but here
> > > goes.
> > >
> > > I'm working on a utility that has to, among many other things, create
> > > directory paths, often with a series of parent directories that may
> > > not already exist.  Solaris has mkdirp(3GEN) in the libgen library,
> > > but I can't find a library call that will do this in FreeBSD.  Kind
> > > of like `mkdir -p` would.
> > >
> > > I know it would be pretty trivial to roll my own, and if I can't find
> > > it I will.  I'm just curious if anyone knows of an *existing* library
> > > call that would do this.
> > >
> > > TIA
> > > Lou
> > 
> > Assuming your working in C what is wrong with:
> > 
> > char command[]	= "mkdir -p /path/to/whatever";
> > 
> > system( command );
> 
> Nothing, except that calling a system command from C when you can roll
> your own method in about 18 lines of code is usually not ideal.
> Particularly when speed is important.  And yes, it is definitely
> important - disk access can be an insurmountable bottleneck for high
> volume systems if it is neglected at the implemenation stage.
> 
> I only wanted a system lib call because I trust FreeBSDs implementation
> to be faster than my quick throw together.
> 
> I've already written it.  It's not pretty, and probably not as fast as a
> system lib would be (it has to make 1 system call per directory in the
> path, rather than just one system call for the whole path).  It is,
> however, much faster than a call to system() would be.

Actually, the mkdirp(3GEN) library routine in Solaris probably makes the
same amount of system calls as your implementation:

> uname -sr
SunOS 5.9
> cat mkdirp.c
#include <libgen.h>
#include <sys/stat.h>

#define path "/tmp/a/b/c/d"

int main(void) {
        mkdirp(path,S_IRWXU);
}

> gcc -lgen -o mkdirp mkdirp.c
> truss ./mkdirp |& tail -10
mkdir("/tmp/a/b/c/d", 0700)                     Err#2 ENOENT
access("/tmp/a/b/c", 0)                         Err#2 ENOENT
access("/tmp/a/b", 0)                           Err#2 ENOENT
access("/tmp/a", 0)                             Err#2 ENOENT
access("/tmp", 0)                               = 0
mkdir("/tmp/a", 0700)                           = 0
mkdir("/tmp/a/b", 0700)                         = 0
mkdir("/tmp/a/b/c", 0700)                       = 0
mkdir("/tmp/a/b/c/d", 0700)                     = 0
_exit(-13163152)


cheers,
Ruben