std::filesystem::exists
Defined in header <filesystem> |
||
---|---|---|
bool exists( std::filesystem::file_status s ) noexcept; |
(1) | (since C++17) |
bool exists( const std::filesystem::path& p ); bool exists( const std::filesystem::path& p, std::error_code& ec ) noexcept; |
(2) | (since C++17) |
Checks if the given file status or path corresponds to an existing file or directory.
1) Equivalent to
status_known(s) && s.type() != file_type::not_found
.
2) Let
s
be a
std::filesystem::file_status
determined as if by
status(p)
or
status(p, ec)
(symlinks are followed), respectively. Returns
exists(s)
. The non-throwing overload calls
ec.clear()
if
status_known(s)
.
Parameters
s | - | file status to check |
p | - | path to examine |
ec | - | out-parameter for error reporting in the non-throwing overload |
Return value
true
if the given path or file status corresponds to an existing file or directory, false
otherwise.
Exceptions
2) The overload that does not take a
std::error_code&
parameter throws
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. Any overload not marked
noexcept
may throw
std::bad_alloc
if memory allocation fails.
Notes
The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling exists(*iterator)
is less efficient than exists(iterator->status())
.
Example
#include <iostream> #include <fstream> #include <cstdint> #include <filesystem> namespace fs = std::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"; else std::cout << " does not exist\n"; } int main() { const fs::path sandbox{"sandbox"}; fs::create_directory(sandbox); std::ofstream{sandbox/"file"}; // create regular file fs::create_symlink("non-existing", sandbox/"symlink"); demo_exists(sandbox); for (const auto& entry : fs::directory_iterator(sandbox)) demo_exists(entry, entry.status()); // use cached status from directory entry fs::remove_all(sandbox); }
Output:
"sandbox" exists "sandbox/symlink" does not exist "sandbox/file" exists
See also
(C++17)(C++17)
|
determines file attributes determines file attributes, checking the symlink target (function) |
(C++17)
|
represents file type and permissions (class) |
checks whether directory entry refers to existing file system object (public member function of std::filesystem::directory_entry ) |
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