Boost :: filesystem that recursively gets the size of each file
Why does this code throw an error when the argument is a directory?
Using boost::recursive_directory_iterator
and using operators std::cout
, I see that it never prints the directory; only files. But, when I try to call boost::filesystem::file_size()
, the error comes up basically saying that I am trying to get the size of a file in a directory.
Error (argument "/ home" ):
terminate called after throwing an instance of 'boost::filesystem::filesystem_error'
what(): boost::filesystem::file_size: Operation not permitted: "/home/lost+found"
Aborted
#include <iostream>
#include <boost/filesystem.hpp>
namespace fs = boost::filesystem;
int main(int argc, char* argv[])
{
if (argc != 2) return -1;
const fs::path file{argv[1]};
if (!fs::exists(file)) return -1;
if (fs::is_regular_file(file))
std::cout << file << " [ " << fs::file_size(file) << " ]\n";
else if (fs::is_directory(file))
for (const fs::directory_entry& f : fs::recursive_directory_iterator{file})
std::cout << f.path().filename() << " [ " << fs::file_size(f.path()) << " ]\n";
}
Compiled with: g++ -Wall -Wextra -pedantic-errors -std=c++14 -lboost_system -lboost_filesystem -O2 -Os -s test3.cpp -o test3
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You will receive an error:
call completion after calling instance 'boost :: filesystem :: filesystem_error' what (): boost :: filesystem :: file_size: operation not allowed: "/ home / lost + found" Canceled
This means that it cannot get the size of / home / lost + found. Usually lost + found folder and file_size
only get the size of regular files .
I understand that the loop does not show the name of this folder. Perhaps this is because the compiler is evaluating fs::file_size(f.path())
and throwing a pre-call exception operator<<
for the filename so that it won't print.
I think the loop needs to be changed to check the regular file before asking for the size:
for (const fs::directory_entry& f : fs::recursive_directory_iterator{file}) {
if (fs::is_regular_file(f.path()) {
std::cout << f.path().filename() << " [ " << fs::file_size(f.path()) << " ]\n";
}
}
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Try to actually get the size recursively:
size_t du(fs::path p) {
return fs::is_regular_file(p)
? file_size(p)
: boost::accumulate(fs::directory_iterator{p}, 0ull, [](auto a, auto p){return a+du(p);});
}
This will work for directories by summing ( accumulate
) files in all base directories.
#include <iostream>
#include <boost/filesystem.hpp>
#include <boost/range/numeric.hpp>
namespace fs = boost::filesystem;
size_t du(fs::path p) {
std::cout << __FUNCTION__ << "(" << p << ")\n";
return fs::is_regular_file(p)
? file_size(p)
: boost::accumulate(fs::directory_iterator{p}, 0ull, [](auto a, auto p){return a+du(p);});
}
int main(int argc, char* argv[])
{
if (argc != 2) return -1;
std::cout << "Size is " << du(argv[1]) << "\n";
}
With debug enabled std::cout
:
Size is du(".")
du("./main.cpp")
du("./a.out")
22435
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