>/$ cmd //c echo hello />/hello />//>/which works, and this, which doesn't: />//>/$ cmd /c echo
hello />//>/Microsoft Windows [Version 10.0.blah] />/(c) Microsoft Corporation. All rights reserved.
/>//>/C:\msys64\home\myname> /
Your example seems to be inverted, the first form doesn't work, the
second does with the same results you show (but inverted).
It would be better if you document how you executed those commands,
we're assuming a mintty terminal running a bash shell, but I haven't
followed all your messages and it might be a cmd window; results
shouldn't change anyway, but for completeness sake.
More details for you, then:
>/I just re-installed msys2 and tried a few things, with interesting
result. /
I install msys2-x86_64-20210604.exe (downloaded last week) from the
msys2 website, and accept all defaults during installation, including
the "run msys2 now" on the final installation screen (which, yes, opens
a mintty terminal running msys2's bash shell). All commands are executed
in that same mintty window immediately following a fresh installation.
So here is the output, cut-and-pasted from that mintty terminal:
dietmar@laptop MSYS ~
$ cmd //c echo hello
hello
dietmar@laptop MSYS ~
$ cmd /c echo hello
Microsoft Windows [Version 10.0.19043.1055]
(c) Microsoft Corporation. All rights reserved.
C:\msys64\home\dietmar>
As you can see, the first form DOES INDEED work, and the second does
not. Why not try it yourself? You will likely have the same results.
No, wrong, cmd is getting an argument which it interprets as it seems
fit, no hack there. The same applies to the ls example before, ls
receives an argument which is expected to be a path, nothing strange.
To find out what cmd is really doing, I believe the authoritative answer
would be given by Microsoft's Command Prompt:
Microsoft Windows [Version 10.0.19043.1055]
(c) Microsoft Corporation. All rights reserved.
C:\Users\dietmar>cmd //c echo hello
Microsoft Windows [Version 10.0.19043.1055]
(c) Microsoft Corporation. All rights reserved.
C:\Users\dietmar>exit
C:\Users\dietmar>
Here we see that cmd.exe //c starts a subshell, rather than executing a
single command.
However, in msys2's mintty/bash window, that same syntax works differently:
dietmar@laptop MSYS ~
$ cmd //c echo hello
hello
dietmar@laptop MSYS ~
$ cmd ///c echo hello
Microsoft Windows [Version 10.0.19043.1055]
(c) Microsoft Corporation. All rights reserved.
C:\msys64\home\dietmar>exit
exit
dietmar@laptop MSYS ~
$ cmd ////c echo hello
hello
dietmar@laptop MSYS ~
$ cmd //////c echo hello
hello
dietmar@laptop MSYS ~
$ cmd ////////c echo hello
hello
dietmar@laptop MSYS ~
$ cmd /////////c echo hello
Microsoft Windows [Version 10.0.19043.1055]
(c) Microsoft Corporation. All rights reserved.
C:\msys64\home\dietmar>exit
exit
dietmar@laptop MSYS ~
$
It seems evident that msys2 is performing slash escaping - ie. 2
consecutive slashes are consolidated into a single slash (rather like
quote escaping in various languages - eg. SQL, CSV, C#, YAML)
recursively (ie. repeatedly) during argument evaluation.
Again, why not simply change this to a form that works without the slash
hackery?
dietmar@laptop MSYS ~
$ cmd /c "echo hello"
hello
>/Interestingly, />//>/ls //c />//>/hangs under msys2 (as well as cygwin), /
Expected as the documentation link describes, //c is taken as a path to
a server, you already knew that.
>/whereas />//>/cmd //c />//>/does not; so it almost seems like msys2 has a hack
to recognize that />/cmd.exe is being invoked ... /
No, wrong, cmd is getting an argument which it interprets as it seems
fit, no hack there. The same applies to the ls example before, ls
receives an argument which is expected to be a path, nothing strange.
>/However, both of the following also complete successfully under msys2, />/WITHOUT the double-slash hack: />//>/$ cmd /c "echo hello" />/hello />//>/$ cmd "/c" "echo hello" />/hello />//>/Both seem preferable to bad syntax. />//>/Of course, there's always the question of why libtool is using cmd.exe />/instead of /bin/echo, which seems to work just fine ... />//>/$ /bin/echo "hello world" />/hello world /--
R.Berber
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