May 26, 2018
Implementation of AT&T Research UNIX V8 newer(1)
There doesn’t appear to be any decent way to compare the last modified times of files from the shell…
Before everybody starts inventing their own names for this, it should be noted that V8 already has a program for this, newer1. It takes two filenames as arguments, and exits with status 0 if and only if either a the first exists and the second does not, or b both exist and the first’s modification time is at least as recent as the second’s. Other- wise it exits with non-zero status. The preceding two sentences are essentially the whole of the manual page for it.
Relatively few people have V8, but in the absence of any other precedent for what this facility should like look, it seems reasonable to follow V8’s lead
newer file1 file2
exit with 0 status if file1 exists and file2 does not, or if file1’s last modified time is at least as recent as file2’s.