std::experimental::filesystem::directory_entry::status, (3) - Linux Manuals

std::experimental::filesystem::directory_entry::status,: std::experimental::filesystem::directory_entry::status,

NAME

std::experimental::filesystem::directory_entry::status, - std::experimental::filesystem::directory_entry::status,

Synopsis

file_status status() const;                         (1) (filesystem TS)
file_status status( error_code& ec ) const;
file_status symlink_status() const;                 (2) (filesystem TS)
file_status symlink_status( error_code& ec ) const;

1) Returns the potentially cached status of the entry, as if determined by a status
call (symlinks are followed to their targets)
2) Returns the potentially cached status of the entry, as if determined by a
symlink_status call (symlinks are not followed)

Parameters

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

Return value

The status of the file referred to by the entry.

Exceptions

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

Notes

The file status information is usually provided as a byproduct of directory
iteration, in which case it is cached and may be obtained by these member functions
without the cost of an additional system call. During directory iteration, calling
status is unnecessary and accessors such as is_directory should be called with the
cached status value, not with a path.

Example

// Run this code

 #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