std::filesystem::create_directory, std::filesystem::create_directories

C++

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Filesystem library (C++17)

Technical Specifications

Filesystem library

Classes
filesystem::path filesystem::filesystem_error filesystem::directory_entry filesystem::directory_iterator filesystem::recursive_directory_iterator filesystem::file_status	filesystem::space_info filesystem::file_type filesystem::perms filesystem::perm_options filesystem::copy_options filesystem::directory_options filesystem::file_time_type
Functions
filesystem::absolute filesystem::canonicalfilesystem::weakly_canonical filesystem::relativefilesystem::proximate filesystem::copy filesystem::copy_file filesystem::copy_symlink filesystem::create_directory filesystem::create_directories filesystem::create_hard_link filesystem::create_symlink filesystem::create_directory_symlink filesystem::current_path	filesystem::exists filesystem::equivalent filesystem::file_size filesystem::hard_link_count filesystem::last_write_time filesystem::permissions filesystem::read_symlink filesystem::remove filesystem::remove_all filesystem::rename filesystem::resize_file filesystem::space filesystem::status filesystem::symlink_status filesystem::temp_directory_path
File types
filesystem::is_block_file filesystem::is_character_file filesystem::is_directory filesystem::is_empty filesystem::status_known	filesystem::is_fifo filesystem::is_other filesystem::is_regular_file filesystem::is_socket filesystem::is_symlink

Defined in header <filesystem>
bool create_directory( const std::filesystem::path& p ); bool create_directory( const std::filesystem::path& p, std::error_code& ec ) noexcept;	(1)	(since C++17)
bool create_directory( const std::filesystem::path& p, const std::filesystem::path& existing_p ); bool create_directory( const std::filesystem::path& p, const std::filesystem::path& existing_p, std::error_code& ec ) noexcept;	(2)	(since C++17)
bool create_directories( const std::filesystem::path& p ); bool create_directories( const std::filesystem::path& p, std::error_code& ec );	(3)	(since C++17)

1) Creates the directory p as if by POSIX mkdir() with a second argument of static_cast<int>(std::filesystem::perms::all) (the parent directory must already exist). If p already exists, the function does nothing (this condition is not treated as an error).

2) Same as (1), except that the attributes of the new directory are copied from existing_p (which must be a directory that exists). It is OS-dependent which attributes are copied: on POSIX systems, the attributes are copied as if by

stat(existing_p.c_str(), &attributes_stat)
mkdir(p.c_str(), attributes_stat.st_mode)

On Windows OS, no attributes of existing_p are copied.

3) Executes (1) for every element of p that does not already exist. If p already exists, the function does nothing (this condition is not treated as an error).

The non-throwing overloads return false if any error occurs.

Parameters

p	-	the path to the new directory to create
existing_p	-	the path to a directory to copy the attributes from
ec	-	out-parameter for error reporting in the non-throwing overload

Return value

true if a directory was created for the directory p resolves to, false otherwise.

Exceptions

1,3) The overload that does not take a std::error_code& parameter throws 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. The overload taking a std::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. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

2) The overload that does not take a std::error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first path argument, existing_p as the second path argument, and the OS error code as the error code argument. The overload taking a std::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. Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

Notes

The attribute-preserving overload (2) is implicitly invoked by copy() when recursively copying directories. Its equivalent in boost.filesystem is copy_directory (with argument order reversed)

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2935	C++17	error if target already exists but isn't a directory	not error
LWG 3014	C++17	error_code overload of create_directories marked noexcept but can allocate memory	noexcept removed

Example

Run this code

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <filesystem>
namespace fs = std::filesystem;

int main()
{
    fs::create_directories("sandbox/1/2/a");
    fs::create_directory("sandbox/1/2/b");
    fs::permissions("sandbox/1/2/b", fs::perms::remove_perms | fs::perms::others_all);
    fs::create_directory("sandbox/1/2/c", "sandbox/1/2/b");
    std::system("ls -l sandbox/1/2");
    fs::remove_all("sandbox");
}

Possible output:

drwxr-xr-x 2 user group 4096 Apr 15 09:33 a
drwxr-x--- 2 user group 4096 Apr 15 09:33 b
drwxr-x--- 2 user group 4096 Apr 15 09:33 c

See also

create_symlinkcreate_directory_symlink (C++17)(C++17)	creates a symbolic link (function)
copy (C++17)	copies files or directories (function)
perms (C++17)	identifies file system permissions (enum)