Cygwin cygdrive prefix test

[p5pRT]

Migrated from rt.perl.org#126834 (status was 'resolved')

Searchable as RT126834$

[p5pRT]

From Stromeko@nexgo.de

The test for the cygdrive prefix can be simplified by using the cygpath
executable instead of parsing the output from df or mount. An
alternative for modern Cygwin would be to use

my $prefix2 = readlink "/proc/cygdrive"

if a fork and some parsing should be avoided and supporting older Cygwin
versions is not considered important.

[p5pRT]

From Stromeko@nexgo.de

perl.fix-636efde.patch

--- t/lib/cygwin.t.orig	2015-12-06 18:29:01.970308000 +0100
+++ t/lib/cygwin.t	2015-12-06 18:44:29.329880800 +0100
@@ -51,18 +51,14 @@
 
 # Cygdrive mount prefix
 my @flags = split(/,/, Cygwin::mount_flags('/cygdrive'));
-my $prefix = pop(@flags);
-ok($prefix, "cygdrive mount prefix = " . (($prefix) ? $prefix : '<none>'));
-chomp(my $prefix2 = `df -a | grep -i '^c: ' | cut -d% -f2 | xargs`);
-# we get something like "C: - - - - /cygdrive" if this isn't the entry
-# df displays free space info for
-$prefix2 =~ s/.* //;
-$prefix2 =~ s/\/c$//i;
+my $prefix1 = pop(@flags);
+ok($prefix1, "cygdrive mount prefix1 = " . (($prefix1) ? $prefix1 : '<none>'));
+chomp(my $prefix2 = `cygpath C:`); # the drive need not actually exist, so this will always work
+$prefix2 =~ s/\/c$//;
+$prefix2 = "/" unless $prefix2;
 SKIP:
 {
-    $prefix2
-       or skip("No C: entry found in df output", 1);
-    is($prefix, $prefix2, 'cygdrive mount prefix');
+    is($prefix1, $prefix2, 'cygdrive mount prefix2 = ' . $prefix2);
 }
 
 my @mnttbl = Cygwin::mount_table();

[p5pRT]

From Stromeko@nexgo.de

Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Wavetables for the Terratec KOMPLEXER​:
http​://Synth.Stromeko.net/Downloads.html#KomplexerWaves

[p5pRT]

From @tonycoz

On Sun Dec 06 09​:57​:49 2015, Stromeko@​nexgo.de wrote​:

The test for the cygdrive prefix can be simplified by using the cygpath
executable instead of parsing the output from df or mount. An
alternative for modern Cygwin would be to use

my $prefix2 = readlink "/proc/cygdrive"

if a fork and some parsing should be avoided and supporting older Cygwin
versions is not considered important.

The change looks sane, though I'm not sure why you renamed $prefix.

Can you supply this patch as a "git format-patch" style patch?

Tony

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From Stromeko@nexgo.de

Tony Cook via RT writes​:

The change looks sane, though I'm not sure why you renamed $prefix.

Just for symmetry reasons, but I have no problem with keeping it named
just $prefix.

Can you supply this patch as a "git format-patch" style patch?

Can do.

Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Samples for the Waldorf Blofeld​:
http​://Synth.Stromeko.net/Downloads.html#BlofeldSamplesExtra

[p5pRT]

From Stromeko@nexgo.de

Tony Cook via RT writes​:

Can you supply this patch as a "git format-patch" style patch?

Attached.

[p5pRT]

From Stromeko@nexgo.de

0001-perl-126834-Cygwin-cygdrive-prefix-test.patch

From b12ceb2c68415fbe6e46390f71870fb73854f24a Mon Sep 17 00:00:00 2001
From: Achim Gratz <Stromeko@NexGo.DE>
Date: Mon, 7 Dec 2015 19:42:37 +0100
Subject: [PATCH] [perl #126834] Cygwin cygdrive prefix test

* t/lib/cygwin.t: The test for the cygdrive prefix is simplified by
using the cygpath executable instead of parsing the output from df or
mount.

An alternative for modern Cygwin would be to use

my $prefix2 = readlink "/proc/cygdrive"

if a fork and some parsing should be avoided and supporting older Cygwin
versions is not considered important.
---
 t/lib/cygwin.t | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/t/lib/cygwin.t b/t/lib/cygwin.t
index 9033d3f..174f3bd 100644
--- a/t/lib/cygwin.t
+++ b/t/lib/cygwin.t
@@ -52,13 +52,14 @@ is(Cygwin::mount_flags("/cygdrive") =~ /,cygdrive/,  1, "check cygdrive mount_fl
 # Cygdrive mount prefix
 my @flags = split(/,/, Cygwin::mount_flags('/cygdrive'));
 my $prefix = pop(@flags);
-ok($prefix, "cygdrive mount prefix = " . (($prefix) ? $prefix : '<none>'));
-chomp(my $prefix2 = `df | grep -i '^c: ' | cut -d% -f2 | xargs`);
-$prefix2 =~ s/\/c$//i;
-if (! $prefix2) {
-    $prefix2 = '/';
+ok($prefix, "cygdrive mount prefix  = " . (($prefix) ? $prefix : '<none>'));
+chomp(my $prefix2 = `cygpath C:`); # the drive need not actually exist, so this will always work
+$prefix2 =~ s/\/c$//;
+$prefix2 = "/" unless $prefix2;
+SKIP:
+{
+    is($prefix, $prefix2, 'cygdrive mount prefix2 = ' . $prefix2);
 }
-is($prefix, $prefix2, 'cygdrive mount prefix');
 
 my @mnttbl = Cygwin::mount_table();
 ok(@mnttbl > 0, "non empty mount_table");
-- 
2.6.2

[p5pRT]

From Stromeko@nexgo.de

Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

SD adaptation for Waldorf rackAttack V1.04R1​:
http​://Synth.Stromeko.net/Downloads.html#WaldorfSDada

[p5pRT]

From vano@mail.mipt.ru

`cygpath C​:\' isn't completely fool-proof as C​:\ might be mounted independently.
(you decide if it's fool-proof enough for the case at hand)

`readlink /proc/cygdrive' does look like the best solution.

So, the best way I see is to use it and fall back to the heuristics if it's
missing.

"Shelling out" can't be avoided unless you wish to check the registry by hand​:
initially (in 2000), there was no dedicated utility to read the prefix at all,
the docs pointed directly to the registry
(http​://web.archive.org/web/20001213205800/http​://www.cygwin.com/cygwin-ug-net/using.html;
http​://web.archive.org/web/20001213195700/http​://www.cygwin.com/cygwin-ug-net/using-utils.html#MOUNT).

I'll now check the Cygwin repo for /proc/cygdrive addition time vs. registry
setting elimination time to see if one can avoid the heuristics entirely and
skip from the former directly to the latter.

--
Best regards,
Ivan mailto​:vano@​mail.mipt.ru

[p5pRT]

From Stromeko@nexgo.de

Ivan Pozdeev via perl5-porters writes​:

`cygpath C​:\' isn't completely fool-proof as C​:\ might be mounted independently.
(you decide if it's fool-proof enough for the case at hand)

In which case the former code would fail just the same. If you wanted,
you could loop through all 26 drive letters and see which prefix comes
up the most often and pick that as the cygdrive prefix, but it could
still fail in some contrived situations.

`readlink /proc/cygdrive' does look like the best solution.

So, the best way I see is to use it and fall back to the heuristics if it's
missing.

Well, I can get behind that idea; thanks for mentioning. How about the
attached?

[p5pRT]

From Stromeko@nexgo.de

0001-perl-126834-Cygwin-cygdrive-prefix-test.patch

From bcfee9939cab7b09a129ee72db7281c27d1ff9c3 Mon Sep 17 00:00:00 2001
From: Achim Gratz <Stromeko@NexGo.DE>
Date: Mon, 7 Dec 2015 19:42:37 +0100
Subject: [PATCH] [perl #126834] Cygwin cygdrive prefix test

* t/lib/cygwin.t: Use the /proc virtual filesystem to determine the
  cygdrive prefix.  If that isn't available, fall back to using the
  cygpath executable instead of parsing the output from df or mount
  for older Cygwin.  That fallback can fail if C:\ is manually mounted
  someplace else, but the former code had the same problem.
---
 t/lib/cygwin.t | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/t/lib/cygwin.t b/t/lib/cygwin.t
index 9033d3f..dd2e31e 100644
--- a/t/lib/cygwin.t
+++ b/t/lib/cygwin.t
@@ -52,13 +52,16 @@ is(Cygwin::mount_flags("/cygdrive") =~ /,cygdrive/,  1, "check cygdrive mount_fl
 # Cygdrive mount prefix
 my @flags = split(/,/, Cygwin::mount_flags('/cygdrive'));
 my $prefix = pop(@flags);
-ok($prefix, "cygdrive mount prefix = " . (($prefix) ? $prefix : '<none>'));
-chomp(my $prefix2 = `df | grep -i '^c: ' | cut -d% -f2 | xargs`);
-$prefix2 =~ s/\/c$//i;
-if (! $prefix2) {
-    $prefix2 = '/';
+ok($prefix, "cygdrive mount prefix  = " . (($prefix) ? $prefix : '<none>'));
+my $prefix2 = readlink "/pro/cygdrive";
+unless ($prefix2) {
+    # fallback to old Cygwin, the drive need not actually exist, so
+    # this will always work (but might return the wrong prefix if the
+    # user re-mounted C:\
+    chomp($prefix2 = `cygpath C:`);
+    $prefix2 = substr($prefix2, 0, -1-(length($prefix2)>2));
 }
-is($prefix, $prefix2, 'cygdrive mount prefix');
+is($prefix, $prefix2, 'cygdrive mount prefix2 = ' . $prefix2);
 
 my @mnttbl = Cygwin::mount_table();
 ok(@mnttbl > 0, "non empty mount_table");
-- 
2.6.2

[p5pRT]

From Stromeko@nexgo.de

Regards,
Achim.
--
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

Factory and User Sound Singles for Waldorf Q+, Q and microQ​:
http​://Synth.Stromeko.net/Downloads.html#WaldorfSounds

[p5pRT]

From Stromeko@nexgo.de

Achim Gratz writes​:

Well, I can get behind that idea; thanks for mentioning. How about the
attached?

Sorry, the patch still had a change in I made to test the fallback…
Here's the correct one.

[p5pRT]

From Stromeko@nexgo.de

0001-perl-126834-Cygwin-cygdrive-prefix-test.patch

From bcfee9939cab7b09a129ee72db7281c27d1ff9c3 Mon Sep 17 00:00:00 2001
From: Achim Gratz <Stromeko@NexGo.DE>
Date: Mon, 7 Dec 2015 19:42:37 +0100
Subject: [PATCH] [perl #126834] Cygwin cygdrive prefix test

* t/lib/cygwin.t: Use the /proc virtual filesystem to determine the
  cygdrive prefix.  If that isn't available, fall back to using the
  cygpath executable instead of parsing the output from df or mount
  for older Cygwin.  That fallback can fail if C:\ is manually mounted
  someplace else, but the former code had the same problem.
---
 t/lib/cygwin.t | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/t/lib/cygwin.t b/t/lib/cygwin.t
index 9033d3f..dd2e31e 100644
--- a/t/lib/cygwin.t
+++ b/t/lib/cygwin.t
@@ -52,13 +52,16 @@ is(Cygwin::mount_flags("/cygdrive") =~ /,cygdrive/,  1, "check cygdrive mount_fl
 # Cygdrive mount prefix
 my @flags = split(/,/, Cygwin::mount_flags('/cygdrive'));
 my $prefix = pop(@flags);
-ok($prefix, "cygdrive mount prefix = " . (($prefix) ? $prefix : '<none>'));
-chomp(my $prefix2 = `df | grep -i '^c: ' | cut -d% -f2 | xargs`);
-$prefix2 =~ s/\/c$//i;
-if (! $prefix2) {
-    $prefix2 = '/';
+ok($prefix, "cygdrive mount prefix  = " . (($prefix) ? $prefix : '<none>'));
+my $prefix2 = readlink "/proc/cygdrive";
+unless ($prefix2) {
+    # fallback to old Cygwin, the drive need not actually exist, so
+    # this will always work (but might return the wrong prefix if the
+    # user re-mounted C:\
+    chomp($prefix2 = `cygpath C:`);
+    $prefix2 = substr($prefix2, 0, -1-(length($prefix2)>2));
 }
-is($prefix, $prefix2, 'cygdrive mount prefix');
+is($prefix, $prefix2, 'cygdrive mount prefix2 = ' . $prefix2);
 
 my @mnttbl = Cygwin::mount_table();
 ok(@mnttbl > 0, "non empty mount_table");
-- 
2.6.2