std::experimental::filesystem::exists
From cppreference.com
| Defined in header <experimental/filesystem>
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bool exists( file_status s )
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(1) | (filesystem TS) |
bool exists( const path& p );
bool exists( const path& p, error_code& ec )
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(2) | (filesystem TS) |
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) Equivalent to
exists(status(p)) or exists(status(p, ec)) (symlinks are followed). The non-throwing overload returns false if an error occurs.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
1)
noexcept specification:
noexcept2) The overload that does not take an
error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p 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 an 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. This overload has noexcept specification:
noexceptNotes
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
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";
else
std::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
See also
| determines file attributes determines file attributes, checking the symlink target (function) | |
| represents file type and permissions (class) | |
| 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)
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