NAME¶

std::filesystem::directory_entry::is_socket - std::filesystem::directory_entry::is_socket

Synopsis¶

bool is_socket() const; (1) (since C++17)
bool is_socket( std::error_code& ec ) const noexcept; (2) (since C++17)

Checks whether the pointed-to object is a named socket. Effectively returns:

1) std::filesystem::is_socket(status()),
2) std::filesystem::is_socket(status(ec)).

Parameters¶

ec - out-parameter for error reporting in the non-throwing overload

Return value¶

true if the referred-to filesystem object is a named socket, false otherwise.

Exceptions¶

Any overload not marked noexcept may throw std::bad_alloc if memory allocation
fails.

1) Throws std::filesystem::filesystem_error on underlying OS API errors, constructed
with p as the first path argument and the OS error code as the error code argument.
2) Sets a std::error_code& parameter to the OS API error code if an OS API call
fails, and executes ec.clear() if no errors occur.

Example¶

// Run this code

#include <cstdio>
#include <cstring>
#include <filesystem>
#include <fstream>
#include <functional>
#include <iostream>
#include <memory>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <unistd.h>

namespace fs = std::filesystem;

void print_entry_type(const std::filesystem::directory_entry& entry)
{
std::cout << entry.path() << ": ";

if (!entry.exists())
std::cout << "does not exist ";
if (entry.is_block_file())
std::cout << "is a block device ";
if (entry.is_character_file())
std::cout << "is a character device ";
if (entry.is_directory())
std::cout << "is a directory ";
if (entry.is_fifo())
std::cout << "is a named IPC pipe ";
if (entry.is_regular_file())
std::cout << "is a regular file ";
if (entry.is_socket())
std::cout << "is a named IPC socket ";
if (entry.is_symlink())
std::cout << "(a symlink)";
if (entry.is_other())
std::cout << "(an `other` file)";

std::cout << '\n';
}

template<typename Type, typename Fun>
class scoped_cleanup
{
std::unique_ptr<Type, std::function<void(const Type*)>> u;

public:
scoped_cleanup(Type* ptr, Fun fun) : u{ptr, std::move(fun)} {}
};

int main()
{
// Create files of different kinds.
std::filesystem::current_path(fs::temp_directory_path());
const std::filesystem::path sandbox{"sandbox"};
scoped_cleanup remove_all_at_exit{&sandbox, [](const fs::path* p)
{
std::cout << "cleanup: remove_all(" << *p << ")\n";
fs::remove_all(*p);
}};
std::filesystem::create_directory(sandbox);
std::ofstream{sandbox/"file"}; // Creates a regular file
std::filesystem::create_directory(sandbox/"dir");

mkfifo((sandbox/"pipe").string().data(), 0644);
struct sockaddr_un addr; addr.sun_family = AF_UNIX;

std::strcpy(addr.sun_path, (sandbox/"sock").string().data());
int fd{socket(PF_UNIX, SOCK_STREAM, 0)};
scoped_cleanup close_socket_at_exit{&fd, [](const int* f)
{
std::cout << "cleanup: close socket #" << *f << '\n';
close(*f);
}};
bind(fd, reinterpret_cast<sockaddr*>(std::addressof(addr)), sizeof addr);

fs::create_symlink("file", sandbox/"symlink");

for (std::filesystem::directory_entry entry: fs::directory_iterator(sandbox))
print_entry_type(entry);

// Request file system objects status directly:
for (const char* str : {"/dev/null", "/dev/cpu", "/usr/include/c++",
"/usr/include/asm", "/usr/include/time.h"})
print_entry_type(fs::directory_entry{str});

} // Cleanup via scoped_cleanup objects

Possible output:¶

"sandbox/symlink": is a regular file (a symlink)
"sandbox/sock": is a named IPC socket (an `other` file)
"sandbox/pipe": is a named IPC pipe (an `other` file)
"sandbox/dir": is a directory
"sandbox/file": is a regular file
"/dev/null": is a character device (an `other` file)
"/dev/cpu": does not exist
"/usr/include/c++": is a directory
"/usr/include/asm": is a directory (a symlink)
"/usr/include/time.h": is a regular file
cleanup: close socket #3
cleanup: remove_all("sandbox")

See also¶

is_socket checks whether the argument refers to a named IPC socket
(C++17) (function)