How to get the oldest file in a directory using C?

Question

I'm implementing log mechanism and I want to delete oldest log file based on time creating in the directory when reach the defined size.

But now I stuck on getting the oldest file based on time creating. How to get it using C?

Answer 1

There isn't a portable way to get a file's creation time (or its modification time) in C.

Instead you need to rely on something that isn't strictly portable - eg use the file name from the directory entry with the stat() function defined by POSIX, to get a structure that might or might not have a struct timespec st_ctim; field.

Of course some file systems don't have a creation time at all; and even if there is one if you copy a file elsewhere (eg to remote storage) the creation time will be gone, so it's relatively unreliable.

Instead; it's much better to put the creation time and date into the file name. If you do this in the correct order ("year, month, day, hour, minute, second" - eg maybe like " mylog_2019-10-31_14-23-45.txt ") and keep leading zeros (eg 09 for month and never 9 for month) then sorting a list of file names alphanumerically will also sort them chronologically.

Answer 2

you should maintain an internal queue of file name. New one created is added to the head constantly. When need delete, let delete the tail guy