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std::experimental::filesystem::is_socket

From cppreference.com
< cpp‎ | experimental‎ | fs
 
 
Technical specifications
Filesystem library (filesystem TS)
Library fundamentals (library fundamentals TS)
Library fundamentals 2 (library fundamentals 2 TS)
Extensions for parallelism (parallelism TS)
Extensions for concurrency (concurrency TS)
Concepts (concepts TS)
Ranges (ranges TS)
Special mathematical functions (special math TR)
 
 
Defined in header <experimental/filesystem>
bool is_socket( file_status s );
(1) (filesystem TS)
bool is_socket( const path& p );
bool is_socket( const path& p, error_code& ec );
(2) (filesystem TS)

Checks if the given file status or path corresponds to a named IPC socket, as if determined by the POSIX S_IFSOCK.

1) Equivalent to s.type() == file_type::socket.
2) Equivalent to is_socket(status(p)) or is_socket(status(p, ec)).

Contents

[edit] Parameters

s - file status to check
p - path to examine
ec - out-parameter for error reporting in the non-throwing overload

[edit] Return value

true if the file indicated by p or if the type indicated s refers to a named socket. The non-throwing overload returns false if an error occurs.

[edit] Exceptions

1)
noexcept specification:  
noexcept
  
2,3) The overload that does not take a error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first argument and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. The overload taking a error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. This overload has
noexcept specification:  
noexcept
  

[edit] Notes

Named sockets are UNIX domain sockets constructed with socket and bind POSIX APIs, which may be used for advanced interprocess communication. In particular, they may be used to transport open file descriptors from one running process to another.

The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling is_socket(*iterator) is less efficient than is_socket(iterator->status())

[edit] Example

#include <iostream>
#include <fstream>
#include <cstdio>
#include <cstring>
#include <experimental/filesystem>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/stat.h>
 
namespace fs = std::experimental::filesystem;
 
void demo_status(const fs::path& p, fs::file_status s)
{
    std::cout << p;
    // alternative: switch(s.type()) { case fs::file_type::regular: ...}
    if(fs::is_regular_file(s)) std::cout << " is a regular file\n";
    if(fs::is_directory(s)) std::cout << " is a directory\n";
    if(fs::is_block_file(s)) std::cout << " is a block device\n";
    if(fs::is_character_file(s)) std::cout << " is a character device\n";
    if(fs::is_fifo(s)) std::cout << " is a named IPC pipe\n";
    if(fs::is_socket(s)) std::cout << " is a named IPC socket\n";
    if(fs::is_symlink(s)) std::cout << " is a symlink\n";
    if(!fs::exists(s)) std::cout << " does not exist\n";
}
int main()
{
    // create files of different kinds
    fs::create_directory("sandbox");
    std::ofstream("sandbox/file"); // create regular file
    fs::create_directory("sandbox/dir");
    mkfifo("sandbox/pipe", 0644);
    struct sockaddr_un addr;
    addr.sun_family = AF_UNIX;
    std::strcpy(addr.sun_path, "sandbox/sock");
    int fd = socket(PF_UNIX, SOCK_STREAM, 0);
    bind(fd, (struct sockaddr*)&addr, sizeof addr);
    fs::create_symlink("file", "sandbox/symlink");
 
    // demo different status accessors
    for(auto it = fs::directory_iterator("sandbox"); it != fs::directory_iterator(); ++it)
        demo_status(*it, it->symlink_status()); // use cached status from directory entry
    demo_status("dev/null", fs::status("/dev/null")); // direct calls to status
    demo_status("dev/sda", fs::status("/dev/sda"));
    demo_status("sandbox/no", fs::status("/sandbox/no"));
 
    // cleanup
    close(fd);
    fs::remove_all("sandbox");
}

Possible output:

"sandbox/file" is a regular file
"sandbox/dir" is a directory
"sandbox/pipe" is a named IPC pipe
"sandbox/sock" is a named IPC socket
"sandbox/symlink" is a symlink
"dev/null" is a character device
"dev/sda" is a block device
"sandbox/no" does not exist

[edit] See also

determines file attributes
determines file attributes, checking the symlink target
(function) [edit]
represents file type and permissions
(class) [edit]
checks whether file status is known
(function) [edit]
checks whether the given path refers to block device
(function) [edit]
checks whether the given path refers to a character device
(function) [edit]
checks whether the given path refers to a directory
(function) [edit]
checks whether the given path refers to a named pipe
(function) [edit]
checks whether the argument refers to an other file
(function) [edit]
checks whether the argument refers to a regular file
(function) [edit]
checks whether the argument refers to a symbolic link
(function) [edit]
checks whether path refers to existing file system object
(function) [edit]
cached status of the file designated by this directory entry
cached symlink_status of the file designated by this directory entry
(public member function of std::experimental::filesystem::directory_entry) [edit]