From: Eli Zaretskii <eliz@gnu.org>
Date: Mon, 1 Nov 2021 15:09:52 +0000 (+0200)
Subject: Improve documentation of 'file-has-changed-p'
X-Git-Tag: emacs-29.0.90~3671^2~297
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=dfc89318ceddaa6801746f53c400cacb9685aabe;p=emacs.git

Improve documentation of 'file-has-changed-p'

* etc/NEWS:
* doc/lispref/files.texi (File Attributes): Improve wording of the
documentation of 'file-has-changed-p'.
---

diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi
index 250f7a3f9f5..b7420fc678f 100644
--- a/doc/lispref/files.texi
+++ b/doc/lispref/files.texi
@@ -1315,12 +1315,14 @@ on the 19th, @file{aug-20} was written on the 20th, and the file
 @end defun
 
 @defun file-has-changed-p filename
-This convenience function is useful when, for instance, parsing files
-run-time, and you typically want to re-read a file when it has
-changed.  This function returns non-@code{nil} the first time it's
-called on @var{filename} in an Emacs session, but will return
-@code{nil} on subsequent calls in that session (unless the file
-changes its modification time).
+This function returns non-@code{nil} if the time stamp of
+@var{filename} has changed since the last call.  When called for the
+first time for some @var{filename}, it records the last modification
+time of the file and returns non-@code{nil}.  Thereafter, when called
+for the same @var{filename}, it compares the current time stamp with
+the recorded one and returns non-@code{nil} only if they are
+different.  This is useful when a Lisp program wants to re-read a file
+whenever it changes.
 @end defun
 
 @defun file-attributes filename &optional id-format
diff --git a/etc/NEWS b/etc/NEWS
index 114441f1b6a..73f76076d46 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -369,8 +369,8 @@ Use 'exif-parse-file' and 'exif-field' instead.
 +++
 *** New function 'file-has-changed-p'.
 This convenience function is useful when writing code that parses
-files run-time, and allows you to easily re-parse files when they have
-changed (but not otherwise).
+files at run-time, and allows Lisp programs to re-parse files only
+when they have changed.
 
 ---
 *** New function 'font-has-char-p'.