List files in current directory

[Kristan]

Hi there, quick question, how would I retrieve a list of files in ANSI C in
a purely platform independent way?

Any pointers would be great!

thanks
Kristan

["Nils O. Selåsdal"]

Kristan wrote:
> Hi there, quick question, how would I retrieve a list of files in ANSI C in
> a purely platform independent way?

It is not possible, as directories are not a part of ANSI C.

> Any pointers would be great!

Here's a char *, be careful!

[Rod Pemberton]

"Kristan" <kris...@hotmail.com> wrote in message
news:452624ee$0$16554$ed26...@ptn-nntp-reader01.plus.net...

> Hi there, quick question, how would I retrieve a list of files in ANSI C
in
> a purely platform independent way?
>
> Any pointers would be great!
>

(I'm posting after reading on comp.lang.c. I don't know if it's suited to
the other NG's you posted to and you didn't set followups to the NG you are
reading from. Since, I don't know from which NG you are reading replies,
all NG's you posted to whether appropriate or not get this message.)

"in ANSI C"
- You don't. You could use POSIX C routines.

"in a purely platform independent way"

- You might use a platform specific version of Doug Gwyn's Public Domain
libndir package or create a multiplatform version from the various versions.
for BSD, libndir.tar.Z http://ftp.br.xemacs.org/pub/unix-c/languages/c/
for POSIX, libndir-posix.tar.Z
http://ftp.br.xemacs.org/pub/unix-c/languages/c/
for DOS, (several versions exist, I'm not looking them up unless you
_actually_ need them, i.e., beg)
- You might look at how multi-platform applications which store directory
structures work, like Info-ZIP, PDTar (Public Domain tar), GNU tar, etc...
Infozip http://www.info-zip.org/pub/infozip/
pdtar.tar.Z http://ftp.br.xemacs.org/pub/unix-c/tapes/

Programs like Info-ZIP and PDTar have to create their routines which perform
directory access identically on many platforms. However, those routines may
not be integrated into a single file...

Rod Pemberton

[Kristan]

Hi there, well, POSIX sounds promising, as it seems to be supported on Linux
and Windows (2000 upwards), basically I'm using Windows for development and
the Debian Linux server is the platform.

Do you know whether POSIX is available with my Visual Studio 2005 C
compiler? Or would I have to obtain it separately?

thanks
Kristan

"Rod Pemberton" <do_no...@bitfoad.cmm> wrote in message
news:eg5ako$s9o$1...@main.corriga.net...

[Simon Biber]

Kristan wrote:
> Hi there, well, POSIX sounds promising, as it seems to be supported on Linux
> and Windows (2000 upwards), basically I'm using Windows for development and
> the Debian Linux server is the platform.
>
> Do you know whether POSIX is available with my Visual Studio 2005 C
> compiler? Or would I have to obtain it separately?

I don't think it's directly supported. There is a POSIX subsystem for
Windows that you can download, but it does not use the Visual Studio C
compiler.

My approach when dealing with platform-specifics is to abstract the
functionality into functions that are conditionally compiled on each system.

Below is a directory lister for Windows, Unix/POSIX and MS-DOS.

#include <stdio.h>

#ifdef _WIN32

/* Compiling for Windows */

#include <windows.h>

int main(void)
{
WIN32_FIND_DATA f;
HANDLE h = FindFirstFile("./*", &f);
if(h != INVALID_HANDLE_VALUE)
{
do
{
puts(f.cFileName);
} while(FindNextFile(h, &f));
}
else
{
fprintf(stderr, "Error opening directory\n");
}
return 0;
}

#else
#ifdef __unix__

/* Compiling for UNIX / POSIX */

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

int main(void)
{
DIR *dir = opendir(".");
if(dir)
{
struct dirent *ent;
while((ent = readdir(dir)) != NULL)
{
puts(ent->d_name);
}
}
else
{
fprintf(stderr, "Error opening directory\n");
}
return 0;
}

#else
#ifdef __TURBOC__

/* Compiling for MS-DOS */

#include <dir.h>

int main(void)
{
struct ffblk ffblk;
if(findfirst("*.*", &ffblk, 0) == 0)
{
do
{
puts(ffblk.ff_name);
} while(findnext(&ffblk) == 0);
}
else
{
fprintf(stderr, "Error opening directory\n");
}
return 0;
}

#else
#error Unsupported Implementation
#endif
#endif
#endif

[Gordon Burditt]

>Hi there, quick question, how would I retrieve a list of files in ANSI C in
>a purely platform independent way?

1. Prompt the user for the file names, one at a time.
2. Get the list of file names from argv[].
3. Open a file containing a list of file names and read it, one line at a time.

[Joe Wright]

Windows:
system("dir /b > file.lst");
Linux:
system("ls > file.lst");

might do it.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[Keith Thompson]

Joe Wright <joeww...@comcast.net> writes:
> Kristan wrote:
>> Hi there, quick question, how would I retrieve a list of files in
>> ANSI C in a purely platform independent way?
>> Any pointers would be great!
>> thanks
>> Kristan
> Windows:
> system("dir /b > file.lst");
> Linux:
> system("ls > file.lst");
>
> might do it.

Or it might not.

<OT>
In both cases, the command applies only to the current directory,
whatever that happens to be. The Unix command skips any files whose
names start with '.'. The order in which the files are listed may or
may not depend on the current locale. Either command will fail if you
don't have write permission in the current directory. If "file.lst"
already exists, the command will either clobber it or fail; if it
doesn't exist, you've just added a new file that may or may not show
up in the listing.
</OT>

Since you've provided different solutions for Windows and Linux, it's
obviously not "purely platform independent", which is what the OP was
asking for. The fact that you're using the standard function system()
doesn't make the code platform independent; it merely delays any
failure until execution time.

There is no purely platform independent solution.

Both Windows and Linux provide system-specific mechanisms for
retrieving a list of files (the Linux solution should work on any
Unix-like system). These mechanisms are far more flexible, and they
don't depend on creating and reading a temporary file in the very
directory you're trying to examine

This is one of those cases where trying to write portable code is a
waste of time; the non-portable solutions work better, and the
seemingly portable solution isn't portable at all.

--
Keith Thompson (The_Other_Keith) ks...@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Andrew Poelstra]

On Sat, 2006-10-07 at 21:03 +0000, Keith Thompson wrote:
> Kristan wrote:
>> [How can I get a directory listing?]

>
> There is no purely platform independent solution.
>
> Both Windows and Linux provide system-specific mechanisms for
> retrieving a list of files (the Linux solution should work on any
> Unix-like system). These mechanisms are far more flexible, and they
> don't depend on creating and reading a temporary file in the very
> directory you're trying to examine
>
> This is one of those cases where trying to write portable code is a
> waste of time; the non-portable solutions work better, and the
> seemingly portable solution isn't portable at all.
>

However, you can improve portability (in the sense of simplifying the
porting process) by wrapping up the Linux and Windows functions in a
header file.

So, on your Windows system you'd
#include "inc/directories_windows.h"
And on Linux you'd
#include "inc/directories_posix.h"

Both would contain the same functions (for example, something called
"get_dirlisting()"), which would simply call the appropriate
system-dependant function.

That way, porting is simply an act of creating a new header file for the
new system.

--
Andrew Poelstra <http://www.wpsoftware.net/projects/>

[Simon Biber]

Andrew Poelstra wrote:
> However, you can improve portability (in the sense of simplifying the
> porting process) by wrapping up the Linux and Windows functions in a
> header file.
>
> So, on your Windows system you'd
> #include "inc/directories_windows.h"
> And on Linux you'd
> #include "inc/directories_posix.h"
>
> Both would contain the same functions (for example, something called
> "get_dirlisting()"), which would simply call the appropriate
> system-dependant function.
>
> That way, porting is simply an act of creating a new header file for the
> new system.

You should use the same header file for both Windows and Posix versions.

The header file merely declares the externally-visible functions and
objects. It does not define any functions. The externally-visible
functions should be the same for both versions.

The function definitions could be in separate directories_windows.c and
directories_posix.c files. Then you simply compile one .c file or the
other in your project depending on the system.

--
Simon.

[Ben Voigt]

"Kristan" <kris...@hotmail.com> wrote in message

news:452632e7$0$24500$ed2e...@ptn-nntp-reader04.plus.net...

> Hi there, well, POSIX sounds promising, as it seems to be supported on
> Linux and Windows (2000 upwards), basically I'm using Windows for
> development and the Debian Linux server is the platform.
>
> Do you know whether POSIX is available with my Visual Studio 2005 C
> compiler? Or would I have to obtain it separately?

For your specific need, look at:
http://www.two-sdg.demon.co.uk/curbralan/code/dirent/dirent.html