berny/findutils
1
0
Fork 0
mirror of git://git.sv.gnu.org/findutils.git synced 2026-01-28 12:33:21 +01:00
Code Issues Packages Projects Releases Wiki Activity

Indicate that %A@ now includes a sub-second part on many systems

Browse Source
This commit is contained in:
James Youngman
2007-07-02 08:42:10 +00:00
parent ea31bc31bb
commit d6e487e3dd
2 changed files with 9 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
ChangeLog
View File

@@ -63,6 +63,9 @@
* doc/find.texi (Copying A Subset of Files): Added a new worked
example.
* doc/find.texi (Updating A Timestamp File): Indicate that %A@ now
includes a sub-second part on many systems.
2007-06-30 Eric Blake <ebb9@byu.net>
* find/pred.c (pred_timewindow): Avoid gcc warnings.

34
doc/find.texi
View File

@@ -4284,36 +4284,14 @@ value of @code{$newest} if that variable is set, but to
@file{timestamp} otherwise. This ensures that an argument is always
given to the @samp{-r} option of the @code{touch} command.
This approach seems quite efficient, but unfortunately it has a bug.
Many operating systems now keep file modification time information at
a granularity which is finer than one second. Unfortunately the
@samp{%A@@} format for @samp{-printf} only prints a whole-number value
currently; that is, these values are at a one-second granularity.
This means that in our example above, @samp{$newest} will be the name
of a file which is no more than one second older than the newest file,
but may indeed be older.
This approach seems quite efficient, but unfortunately it has a
problem. Many operating systems now keep file modification time
information at a granularity which is finer than one second.
Findutils version 4.3.3 and later will print a fractional part with
%A@@, but older versions will not.
It would be possible to solve this problem with some kind of loop:
@smallexample
while true; do
newest=$(find subdir -newer timestamp -printf "%A@@:%p\n" |
sort -n |
tail -1 |
cut -d: -f2- )
if test -z "$newest" ; then
break
else
touch -r "$newest" timestamp
fi
done
@end smallexample
A better fix for this problem would be to allow the @samp{%A@@} format
to produce a result having a fractional part, too. While this is
planned for GNU @code{find}, it hasn't been done yet.
@subsection Coping with sub-second timestamp resolution
@subsection Solving the problem with make
Another tool which often works with timestamps is @code{make}. We can
use @code{find} to generate a @file{Makefile} file on the fly and then