From cppreference.com
Defined in header
std::filesystem::file_time_typelast_write_time(conststd::filesystem::path&p); (1) (since C++17)std::filesystem::file_time_typelast_write_time(conststd::filesystem::path&p,std::error_code&ec)noexcept; (2) (since C++17)voidlast_write_time(conststd::filesystem::path&p,std::filesystem::file_time_typenew_time); (3) (since C++17)voidlast_write_time(conststd::filesystem::path&p,std::filesystem::file_time_typenew_time,std::error_code&ec)noexcept; (4) (since C++17)1,2) Returns the time of the last modification of p, determined as if by accessing the member st_mtime of the POSIX
(symlinks are followed). The non-throwing overload returns file_time_type::min() on errors.
3,4) Changes the time of the last modification of p, as if by POSIX
(symlinks are followed).
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
1,2) The time of the last modification of p.
3,4) (none)
Exceptions
Any overload not marked noexcept may throw
if memory allocation fails.
1,3) 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.
2,4) Sets a std::error_code& parameter to the OS API error code if an OS API call fails, and executes ec.
() if no errors occur.
Notes
It is not guaranteed that immediately after setting the write time, the value returned by (1,2) is the same as what was passed as the argument to (3,4) because the file system's time may be more granular than
.
Example
Run this code
#include<chrono>#include<filesystem>#include<format>#include<fstream>#include<iostream>usingnamespacestd::chrono_literals;intmain(){autop=std::filesystem::temp_directory_path()/"example.bin";std::ofstream{p.c_str()}.put('a');// create filestd::filesystem::file_time_typeftime=std::filesystem::last_write_time(p);std::cout<<std::format("File write time is {}\n",ftime);// move file write time 1 hour to the futurestd::filesystem::last_write_time(p,ftime+1h);// read back from the filesystemftime=std::filesystem::last_write_time(p);std::cout<<std::format("File write time is {}\n",ftime);std::filesystem::remove(p);}Possible output:
File write time is 2023-09-04 19:33:24.702639224 File write time is 2023-09-04 20:33:24.702639224 See also
(C++17)
represents file time values
(typedef)
gets the time of the last data modification of the file to which the directory entry refers
(public member function of std::filesystem::directory_entry)