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The Go programming language
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I've been writing some code which involves syncing files (like rsync) and it became apparent that under Linux I could read modification times (os.Lstat) with nanosecond precision but only write them with microsecond precision. This difference in precision is rather annoying when trying to discover whether files need syncing or not! I've patched syscall and os to increases the accuracy of of os.Chtimes for Linux and Windows. This involved exposing the utimensat system call under Linux and a bit of extra code under Windows. I decided not to expose the "at" bit of the system call as it is impossible to replicate under Windows, so the patch adds syscall.Utimens() to all architectures along with a ImplementsUtimens flag. If the utimensat syscall isn't available (utimensat was added to Linux in 2.6.22, Released, 8 July 2007) then it silently falls back to the microsecond accuracy version it uses now. The improved accuracy for Windows should be good for all versions of Windows. Unfortunately Darwin doesn't seem to have a utimensat system call that I could find so I couldn't implement it there. The BSDs do, but since they share their syscall implementation with Darwin I couldn't figure out how to define a syscall for *BSD and not Darwin. I've left this as a TODO in the code. In the process I implemented the missing methods for Timespec under Windows which I needed which just happened to round out the Timespec API for all platforms! ------------------------------------------------------------ Test code: http://play.golang.org/p/1xnGuYOi4b Linux Before (1000 ns precision) $ ./utimetest.linux.before z Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST Reading mtime 1344937903123457000: 2012-08-14 10:51:43.123457 +0100 BST Linux After (1 ns precision) $ ./utimetest.linux.after z Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST Reading mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 BST Windows Before (1000 ns precision) X:\>utimetest.windows.before.exe c:\Test.txt Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 GMTDT Reading mtime 1344937903123456000: 2012-08-14 10:51:43.123456 +0100 GMTDT Windows After (100 ns precision) X:\>utimetest.windows.after.exe c:\Test.txt Setting mtime 1344937903123456789: 2012-08-14 10:51:43.123456789 +0100 GMTDT Reading mtime 1344937903123456700: 2012-08-14 10:51:43.1234567 +0100 GMTDT R=golang-dev, alex.brainman, rsc, bradfitz CC=golang-dev https://golang.org/cl/6905057 |
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This is the source code repository for the Go programming language.
For documentation about how to install and use Go,
visit http://golang.org/ or load doc/install.html in your web browser.
After installing Go, you can view a nicely formatted
doc/install.html by running godoc --http=:6060
and then visiting http://localhost:6060/doc/install.html.
Unless otherwise noted, the Go source files are distributed
under the BSD-style license found in the LICENSE file.
--
Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set
the environment variable $GOROOT to the full path of the go
directory (the one containing this README). You can omit the
variable if you unpack it into /usr/local/go, or if you rebuild
from sources by running all.bash (see doc/install.html).
You should also add the Go binary directory $GOROOT/bin
to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might
put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See doc/install.html for more details.