std::filesystem::last_write_time
From cppreference.com
< cpp | filesystem
Defined in header <filesystem>
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std::filesystem::file_time_type last_write_time(const std::filesystem::path& p); std::filesystem::file_time_type last_write_time(const std::filesystem::path& p, |
(1) | (since C++17) |
void last_write_time(const std::filesystem::path& p, std::filesystem::file_time_type new_time); |
(2) | (since C++17) |
1) Returns the time of the last modification of
p
, determined as if by accessing the member st_mtime
of the POSIX stat (symlinks are followed)
The non-throwing overload returns file_time_type::min() on errors.Parameters
p | - | path to examine or modify |
new_time | - | new modification time |
ec | - | out-parameter for error reporting in the non-throwing overload |
Return value
1) The time of the last modification of
p
2) (none)
Exceptions
The overload that does not take a std::error_code& parameter throws filesystem_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 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. This overload has noexcept specification:
noexcept
Notes
It is not guaranteed that immediately after setting the write time, the value returned by (1) is the same as what was passed as the argument to (2) because the file system's time may be more granular than file_time_type
.
Example
Run this code
#include <iostream> #include <chrono> #include <iomanip> #include <fstream> #include <filesystem> namespace fs = std::filesystem; using namespace std::chrono_literals; int main() { fs::path p = fs::current_path() / "example.bin"; std::ofstream(p.c_str()).put('a'); // create file auto ftime = fs::last_write_time(p); std::time_t cftime = decltype(ftime)::clock::to_time_t(ftime); // assuming system_clock std::cout << "File write time is " << std::asctime(std::localtime(&cftime)) << '\n'; fs::last_write_time(p, ftime + 1h); // move file write time 1 hour to the future ftime = fs::last_write_time(p); // read back from the filesystem cftime = decltype(ftime)::clock::to_time_t(ftime); std::cout << "File write time is " << std::asctime(std::localtime(&cftime)) << '\n'; fs::remove(p); }
Possible output:
File write time is Tue Mar 31 19:47:04 2015 File write time is Tue Mar 31 20:47:04 2015
See also
(C++17) |
represents file time values (typedef) |