how to check if a folder is empty

twistadias · 08-11-2008, 03:34 AM

i need to check if a folder is empty. The folder is Desktop/uh
it should return a value like 0(empty) 1(1 or more files)

i need to assign a variable to this value in c++

is this possible?

currently im using

Code:

find -empty

which gives me "."

chrism01 · 08-11-2008, 03:49 AM

Code:

>mkdir tmp
>ls tmp
>ls tmp|wc -l
0

twistadias · 08-11-2008, 04:08 AM

Quote:

Originally Posted by chrism01

Code:

>mkdir tmp
>ls tmp
>ls tmp|wc -l
0

Thank you, that worked perfectly
Now how do i set a variable in c++ to the value returned by

Code:

ls tmp|wc -l

i know that i have to use

Code:

system("BASH code in here");

to run linux commands in c++

matthewg42 · 08-11-2008, 04:37 AM

Shelling out to an external program is rather in efficient - a new process has to be created and all that sort of thing. Better to use existing methods from the c library:

Code:

#include <iostream>
#include <string>
#include <cstdlib>
#include <sys/types.h>
#include <dirent.h>

int countEntriesInDir(const char* dirname)
{
        int n=0;
        dirent* d;
        DIR* dir = opendir(dirname);
        if (dir == NULL) return 0;
        while((d = readdir(dir))!=NULL) n++;
        closedir(dir);
        return n;
}

int main(int argc, char* argv[])
{
        if (argc!=2) exit(1);
        std::cout << "entries in " << argv[1] << ": " << countEntriesInDir(argv[1]) << std::endl;
        return 0;
}

The only thing you need to know is that a directory will always contain 2 entries: "." and ".." - yes even the / directory contains "..". You can easily make a "directoryIsEmpty" function by checking if countEntriesInDir(dir) is two or more than two.

twistadias · 08-11-2008, 04:58 AM

Where can i read about <sys/types.h> and <dirent.h>
it doesnt show up on http://home.att.net/~gobruen/progs/cpp/headers.html

i got it working using this:

Code:

int check;
char is_empty[100];
FILE * output;

output = popen("cd ~/Desktop; ls Data | wc -l","r"); 
fgets (is_empty, 100, output); //write to the char
pclose (output);

check = atoi(is_empty);

if (check == 0){
cout << "The folder is empty" << endl;
exit(0);

is this efficient though?

matthewg42 · 08-11-2008, 05:12 AM

They're part of the the C library, not the C++ standard libraries. See the GNU libc documentation.

Shelling out will work, but it's much harder on the machine. Creating a new shell process is much much more resource hungry than calling the libc opendir readdir and closedir functions.