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Learning Poco: List directories recursively

In this tutorial, we will write a simple utility program for listing directories recursively. Poco provides DirectoryIterator to iterate over all the items contained in a directory. We will also make use of DateTimeFormatter to format the last-modified timestamp in our local time zone instead of the default UTC. This utility mimics the behavior of ls -all.

The Poco here stands for the POCO C++ libraries and is not to be confused with Plain Old CLR Object.

Create a file named rec_dir.cc with the following code:

#include <Poco/DirectoryIterator.h>
#include <Poco/DateTimeFormatter.h>
#include <Poco/LocalDateTime.h>
#include <iostream>
#include <string>

using namespace Poco;
using namespace std;

void rec_dir(const string & path)
{
  DirectoryIterator end;
  for (DirectoryIterator it(path); it != end; ++it)
  {
    cout << (it->isDirectory() ? "d" : "-");
    cout << (it->canRead()     ? "r" : "-");
    cout << (it->canWrite()    ? "w" : "-");
    cout << (it->canExecute()  ? "x" : "-");
    cout << "\t";

    cout << it->getSize() << "\t";

    LocalDateTime lastModified(it->getLastModified());
    cout << DateTimeFormatter::format(lastModified, "%Y-%m-%d %H:%M") << "\t";

    cout << it->path() << (it->isDirectory() ? "/" : it->canExecute() ? "*" : "") << endl;

    if (it->isDirectory())
    {
      rec_dir(it->path());
    }
  }
}

int main(int argc, char **argv)
{
  rec_dir(argc > 1 ? argv[1] : ".");
  return 0;
}

Compile it and run:

$ g++ -o rec_dir rec_dir.cc -lPocoFoundation
$ ./rec_dir
-rwx        14223   2011-09-14 13:34        rec_dir*
drwx        4096    2011-09-14 12:52        testdir/
drwx        4096    2011-09-14 12:52        testdir/dir/
-rw-        941     2011-09-14 13:24        rec_dir.cc
-rw-        0       2011-09-14 12:43        somefile

You may also try ./rec_dir .. or ./rec_dir ~. It’s fun! :–)

The code is simple enough but these classes provided by Poco are powerful. You may check out DirectoryIterator and File for information about other usage.

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