traversing a directory recursively

[krishna chaithanya]

Hi,

I am writing a program in C++/Linux where I need to print the information of files in a directory. I need to show info in this way:

<filename> : <last-modified-time>

I want to show all the filenames (only files, no directories and links). I found an API scandir() but it doesn't do a recursive search. It just gives the info of all the elements in the present directory (irrespective of directory/file/link).

In brief, I need the info as we get when we do "ls -R" from command line.

Please help me if u can.

Thanks and Regards,
krishna

[burschik]

Why don't you look at the source code of "ls"?

[wje_lf]

It seems to me that scandir() might be too complex for your needs. Try these:

opendir()
readdir()
closedir()
stat()

Those, plus your basic skills in string manipulation (for adding to your "current" directory) and recursion, ought to do the trick.

Hope this helps.

[krishna chaithanya]

Thanks!

I got to know about one more function to do the purpose.

ftw()/nftw()

Thanks and Regards,
krishna

[wje_lf]

ftw()/nftw()

Cool! I hadn't even been aware of these.

The only reason you might want to avoid them is if you want to sort the names of the files in a directory before listing them; and, more importantly, if you want to sort the names of the directories in a directory before descending into those directories and listing their files.

You want to do such sorting if you want to mimic

ls -R

If you run this shell script, you'll see an example of how ftw() and nftw() don't sort:

#!/bin/sh

rm -rf tuesdaydir tuesdayprog*

mkdir tuesdaydir
mkdir tuesdaydir/1
mkdir tuesdaydir/3
mkdir tuesdaydir/2
touch tuesdaydir/1/alpha
touch tuesdaydir/1/beta
touch tuesdaydir/2/gamma
touch tuesdaydir/2/delta
touch tuesdaydir/3/epsilon
touch tuesdaydir/3/zeta

cat > tuesdayprog.c <<EOD
#define _XOPEN_SOURCE 500
#include <ftw.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int ftwsub(const char        *fpath,
           const struct stat *sb,
           int                typeflag
          )
{
  printf("%s\n",fpath);

  return 0;

} /* ftwsub() */

int nftwsub(const char        *fpath,
            const struct stat *sb,
            int                typeflag,
            struct FTW        *ftwbuf
           )
{
  printf("%s\n",fpath);

  return 0;

} /* nftwsub() */

int main(void)
{
  char   *version_string_content;

  size_t  version_string_length;

  version_string_length=confstr(_CS_GNU_LIBC_VERSION,NULL,0);

  if(version_string_length<1)
  {
    fprintf(stderr,"first confstr() failure\n");

    return 1;
  }

  version_string_content=malloc(version_string_length);

  if(version_string_content==NULL)
  {
    fprintf(stderr,"malloc() failed\n");

    return 1;
  }

  if(confstr(_CS_GNU_LIBC_VERSION,version_string_content,version_string_length)
     !=version_string_length
    )
  {
    fprintf(stderr,"second confstr() failure\n");

    return 1;
  }

  printf("%s\n",version_string_content);

  printf("*** with ftw() ***\n");

  ftw("tuesdaydir",ftwsub,5);

  printf("*** with nftw() ***\n");

  nftw("tuesdaydir",nftwsub,5,0);

  return 0;

} /* main() */
EOD

gcc -Wall tuesdayprog.c -o tuesdayprog

tuesdayprog

This program visits directory tuesdaydir/3 before it visits directory tuesdaydir/2. Here's the output:

glibc 2.7
*** with ftw() ***
tuesdaydir
tuesdaydir/1
tuesdaydir/1/alpha
tuesdaydir/1/beta
tuesdaydir/3
tuesdaydir/3/epsilon
tuesdaydir/3/zeta
tuesdaydir/2
tuesdaydir/2/gamma
tuesdaydir/2/delta
*** with nftw() ***
tuesdaydir
tuesdaydir/1
tuesdaydir/1/alpha
tuesdaydir/1/beta
tuesdaydir/3
tuesdaydir/3/epsilon
tuesdaydir/3/zeta
tuesdaydir/2
tuesdaydir/2/gamma
tuesdaydir/2/delta