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--- public:stuff [2022/10/01 19:53]
canvon Add page description (for inclusion in :public:start), with a page-internal link to the single existing content, timeout+dd
+++ public:stuff [2022/10/19 00:47] (current)
canvon [Speed test] Fix breaking the following section
@@ Line 1: / Line 1: @@
 ====== Stuff ======
-Some miscellaneous stuff that doesn't fit otherwise into the structure...
+Some miscellaneous stuff that doesn't fit otherwise into [[.:start|the structure]]...
-For example, [[#speed_test|speed test by ''timeout'' + ''dd'']]...
+For example, [[#speed_test|speed test by ''timeout'' + ''dd'']], [[#video_file_comparison_using_mpv|video file comparison using mpv]], [[#windows_fork_problems|Windows fork problems]]...
@@ Line 11: / Line 11: @@
 root@ubuntu:~# timeout --foreground -s INT 60s dd if=/dev/sda bs=4096 of=/dev/null  # ad-hoc USB3 storage speed test...
 </code>
+The idea is to not measure transfer duration of a fixed size, but to let it run through until a fixed time has passed (and then look at the transfer speed). For this, we wrap the ''dd'' invocation into the ''timeout'' command.
+The problem, then, was that ''dd'' didn't output **anything** when run under ''timeout''.
+The solution was to use //both// of ''--foreground'' and ''-s INT'' (after the timeout expires, fire signal SIGINT at the wrapped process) //together//. This restored dd's output-at-end, which will now tell the overall transfer speed, as previously expected.
+===== Video file comparison using mpv =====
+To just get the console output of ''mpv'' where it describes the file played (so we can run a wdiff over the saved outputs of similar files): (Previously, it used to be ''mplayer --identify'' or somesuch.)
+<code>
+$ mpv --vo=null --ao=null --frames=1 ...
+</code>
+===== Windows fork problems =====
+On Windows (Win32 API), a process can well have threads, but no ''fork()''-without-''exec()'' is possible, as processes are created to be separate (spawn?)...
+The CygWin compatibility layer for Linux/UNIX-targetted programs had to work hard to get something similar going: [[https://cygwin.com/cygwin-ug-net/highlights.html#ov-hi-process|CygWin highlights: Process Creation]] (via [[http://blog.rolpdog.com/2020/03/why-no-ansible-controller-for-windows.html|ansible controller heavy user of fork() without exec()]])

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