utimens: check for ctime update

[gnulib.git] / doc / posix-functions / utimensat.texi

diff --git a/doc/posix-functions/utimensat.texi b/doc/posix-functions/utimensat.texi
index 5788af1..85fc218 100644 (file)
--- a/doc/posix-functions/utimensat.texi
+++ b/doc/posix-functions/utimensat.texi
@@ -4,15 +4,54 @@
 
 POSIX specification: @url{http://www.opengroup.org/onlinepubs/9699919799/functions/utimensat.html}
 
-Gnulib module: ---
+Gnulib module: utimensat
 
 Portability problems fixed by Gnulib:
 @itemize
+@item
+This function is missing on some platforms:
+glibc 2.3.6, MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX
+5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw,
+Interix 3.5, BeOS.
+However, the replacement function may end up truncating timestamps to
+less resolution than supported by the file system.  Furthermore, the
+replacement function is not safe to be used in libraries and is not
+multithread-safe.
+@item
+This function returns a bogus value instead of failing with
+@code{ENOSYS} on some platforms:
+Linux kernel 2.6.21.
+@item
+This function fails with @code{ENOSYS} if passed the flag
+@code{AT_SYMLINK_NOFOLLOW} on a regular file:
+Linux kernel 2.6.22.
+@item
+When using @code{UTIME_OMIT} or @code{UTIME_NOW}, some systems require
+the @code{tv_sec} argument to be 0, and don't necessarily handle all
+file permissions in the manner required by POSIX:
+Linux kernel 2.6.25.
+@item
+When using @code{UTIME_OMIT} for the modification time, but specifying
+an access time, some systems fail to update the change time:
+Linux kernel 2.6.32.
 @end itemize
 
 Portability problems not fixed by Gnulib:
 @itemize
 @item
-This function is missing on some platforms:
-glibc 2.3.6, MacOS X 10.3, FreeBSD 6.0, NetBSD 3.0, OpenBSD 3.8, AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin, mingw, Interix 3.5, BeOS.
+On some platforms, timestamps of symbolic links cannot be modified, so
+the replacement fails with @code{ENOSYS} if passed the flag
+@code{AT_SYMLINK_NOFOLLOW} on a symlink.
+@item
+The mere act of using @code{lstat} modifies the access time of
+symlinks on some platforms, so @code{utimensat} with
+@code{AT_SYMLINK_NOFOLLOW} can only effectively change modification time:
+Cygwin.
+@item
+The mere act of using @code{stat} modifies the access time of
+directories on some platforms, so @code{utimensat} can only
+effectively change directory modification time:
+Cygwin 1.5.x.
 @end itemize
+
+The gnulib module fdutimensat provides a similar interface.