New option "--direct-io".

doc/NEWS.md

@@ -1,5 +1,6 @@
-0.0.20230726-UNRELEASED
+0.0.20230727-UNRELEASED
  * feature: new "`--sync`" option to flush cache to disk after every write (related to [GH#6](https://github.com/a-j-wood/pv/issues/6), to improve accuracy when writing to slow disks)
+ * feature: new "`--direct-io`" option to bypass cache - implements [GH#29 "Option to enable *O_DIRECT*"](https://github.com/a-j-wood/pv/issues/29) - requested by Romain Kang, Jacek Wielemborek
  * fix: correct byte prefix size to 2 spaces in rate display, so progress display size remains constant at low transfer rates
  * cleanup: rewrote `configure.in` as per suggestions in newer "`autoconf`" manuals
  * cleanup: replaced `header.in` with one generated by "`autoheader`", moving custom logic to a separate header file "`config-aux.h`"

doc/TODO.md

@@ -26,7 +26,6 @@ Feature requests
  * ([GH#17](https://github.com/a-j-wood/pv/issues/17)) Allow "`-r`" with "`-l`" and "`-n`" to output lines/sec (Roland Kletzing)
  * ([GH#22](https://github.com/a-j-wood/pv/issues/22)) Options to skip input and seek on output (Jason A. Pfeil, Feb 2022)
  * ([GH#25](https://github.com/a-j-wood/pv/issues/25)) Normalise progress to 100% on overrun (Andrej Gantvorg)
- * ([GH#29](https://github.com/a-j-wood/pv/issues/29)) Option to enable *O_DIRECT* (Romain Kang, Jacek Wielemborek)
  * ([GH#35](https://github.com/a-j-wood/pv/issues/35)) Allow decimal values for "`-s`", "`-L`", "`-B`" (Thomas Watson - Aug 2020)
  * ([GH#36](https://github.com/a-j-wood/pv/issues/36)) Ignore *SIGWINCH* (window size change) if "`-w`" / "`-H`" provided
  * ([GH#37](https://github.com/a-j-wood/pv/issues/37)) Allow "`-E`" to take a block size argument so errors cause a skip to the next block (Anthony DeRobertis - Oct 2016)

doc/VERSION

@@ -1 +1 @@
-0.0.20230726-UNRELEASED
+0.0.20230727-UNRELEASED

doc/quickref.1.in

@@ -402,6 +402,17 @@ This has no effect when the output is a pipe.  Using
 .B \-Y
 may improve the accuracy of the progress bar when writing to a slow disk.
 .TP
+.B \-K, \-\-direct-io
+Set the
+.I O_DIRECT
+flag on all inputs and outputs, if it is available.  This will minimise
+the effect of caches, at the cost of performance.  Due to memory alignment
+requirements, it also may cause read or write failures with an error of
+"Invalid argument", especially if reading and writing files across a variety
+of filesystems in a single
+.B @PACKAGE@
+call.  Use this option with caution.
+.TP
 .B \-d PID[:FD], \-\-watchfd PID[:FD]
 Instead of transferring data, watch file descriptor
 .B FD
@@ -661,8 +672,10 @@ home page: <http://www.ivarch.com/programs/pv.shtml>
 .SH "SEE ALSO"
 .BR cat (1),
 .BR dialog (1),
-.BR splice (2)
-
+.BR splice (2),
+.BR open (2)
+(for
+.IR O_DIRECT )
 
 .SH LICENSE
 This is free software, distributed under the ARTISTIC 2.0 license.