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

 

C++

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Concepts library (C++20)

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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 the function fails because p resolves to an existing directory, no error is reported. Otherwise on failure an error is reported.

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).

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
P1164R1	C++17	creation failure caused by an existing non-directory file is not an error	made error

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)