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Difference between revisions of "cpp/filesystem/create directory"

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[[zh:cpp/filesystem/create_directory]]

Revision as of 12:27, 31 March 2017

 
C++
 
Filesystem library
Classes
Functions
File types
 
Defined in header <filesystem>
bool create_directory( const std::filesystem::path& p );
bool create_directory( const std::filesystem::path& p, std::error_code& ec );
 (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 );
 (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 and is already a directory, 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, the attributes are copied as if by 
CreateDirectoryExW(existing_p.c_str(), p.c_str(), 0)
3) Executes (1) for every element of p that does not already exist.

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

Contents

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

1,2) true if directory creation is successful, false otherwise.

Exceptions

1,3) Any overload not marked noexcept may throw std::bad_alloc if memory allocation fails.

The overload that does not take a std::error_code& parameter 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.

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

The overload that does not take a std::error_code& parameter throws std::filesystem::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.

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)

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

(C++17)(C++17)
 creates a symbolic link
(function) [edit]
(C++17)
 copies files or directories
(function) [edit]
(C++17)
 identifies file system permissions
(enum) [edit]
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