std::experimental::filesystem::exists

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Experimental

Technical Specification
Filesystem library(filesystem TS)
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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::copy_options
filesystem::directory_options
filesystem::file_time_type

Functions

filesystem::absolute filesystem::system_complete
filesystem::canonical
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

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Defined in header`<experimental/filesystem>`
bool exists( file_status s)	(1)	(filesystem TS)
bool exists(const path& p); bool exists(const path& p, error_code& ec)	(2)	(filesystem TS)

Checks if the given file status or path corresponds to an existing file or directory.

1) Equivalent tostatus_known(s)&& s.type()!= file_type::not_found.

2) Equivalent toexists(status(p)) orexists(status(p, ec)) (symlinks are followed). The non-throwing overload returnsfalse if an error occurs.

[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 given path or file status corresponds to an existing file or directory,false otherwise.

[edit]Exceptions

noexcept specification:

noexcept

2) The overload that does not take anerror_code& parameter throwsfilesystem_error on underlying OS API errors, constructed withp 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 anerror_code& parameter sets it to the OS API error code if an OS API call fails, and executesec.clear() if no errors occur. This overload has

noexcept specification:

noexcept

[edit]Notes

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

[edit]Example

Run this code

#include <cstdint>#include <experimental/filesystem>#include <fstream>#include <iostream>namespace fs= std::experimental::filesystem; void demo_exists(const fs::path& p, fs::file_status s= fs::file_status{}){std::cout<< p;if(fs::status_known(s)? fs::exists(s): fs::exists(p))std::cout<<" exists\n";elsestd::cout<<" does not exist\n";} int main(){    fs::create_directory("sandbox");std::ofstream("sandbox/file");// create regular file    fs::create_symlink("non-existing","sandbox/symlink");     demo_exists("sandbox");for(auto it= fs::directory_iterator("sandbox"); it!= fs::directory_iterator();++it)        demo_exists(*it, it->status());// use cached status from directory entry    fs::remove_all("sandbox");}

Output:

"sandbox" exists"sandbox/file" exists"sandbox/symlink" does not exist

[edit]See also

statussymlink_status	determines file attributes determines file attributes, checking the symlink target (function)[edit]
file_status	represents file type and permissions (class)[edit]
statussymlink_status	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]