diff options
| -rw-r--r-- | lib/PerlIO.pm | 17 | ||||
| -rw-r--r-- | pod/perlrun.pod | 2 | ||||
| -rw-r--r-- | t/io/layers.t | 13 |
3 files changed, 22 insertions, 10 deletions
diff --git a/lib/PerlIO.pm b/lib/PerlIO.pm index 678a79dd2c..24bc2b2b20 100644 --- a/lib/PerlIO.pm +++ b/lib/PerlIO.pm @@ -224,6 +224,8 @@ This can be used to see the effect of/bugs in the various layers e.g. PERLIO=stdio ./perl harness PERLIO=perlio ./perl harness +For the various value of PERLIO see L<perlrun/PERLIO>. + =head2 Querying the layers of filehandle The following returns the B<names> of the PerlIO layers on a filehandle. @@ -236,20 +238,15 @@ C<perlio>. Under C<stdio> the platform specific low-level I/O (like C<unix>) is not part of the stack, but under C<perlio> (and the experimental C<mmap>) it is. -In platforms of DOS progeny (Win32 being the most prominent) the -lowest level layers are C<unix crlf>, meaning that Perl first uses the -UNIX-style low-level fd layer, and then on top of that a layer that -handles the CRLF translation. - The following table summarizes the default layers on UNIX-like and DOS-like platforms and depending on the setting of the C<$ENV{PERLIO}>: - PERLIO UNIX-like DOS-like + PERLIO UNIX-like DOS-like - none stdio unix crlf - stdio stdio stdio - perlio unix perlio unix perlio - mmap unix mmap unix mmap + none or "" stdio unix crlf + stdio stdio stdio + perlio unix perlio unix perlio + mmap unix mmap unix mmap By default the layers from the input side of the filehandle is returned, to get the output side use the optional C<output> argument: diff --git a/pod/perlrun.pod b/pod/perlrun.pod index e6c8f73fce..2b63c6b056 100644 --- a/pod/perlrun.pod +++ b/pod/perlrun.pod @@ -918,6 +918,8 @@ emphasise their similarity to variable "attributes". But the code that parses layer specification strings (which is also used to decode the PERLIO environment variable) treats the colon as a separator. +An unset or empty PERLIO is equivalent to C<:stdio>. + The list becomes the default for I<all> perl's IO. Consequently only built-in layers can appear in this list, as external layers (such as :encoding()) need IO in order to load them!. See L<"open pragma"|open> for how to add external diff --git a/t/io/layers.t b/t/io/layers.t index 0da804c33f..7ba517a788 100644 --- a/t/io/layers.t +++ b/t/io/layers.t @@ -8,7 +8,10 @@ BEGIN { print "1..0 # Skip: not perlio\n"; exit 0; } + # Makes testing easier. + $ENV{PERLIO} = 'stdio' if exists $ENV{PERLIO} && $ENV{PERLIO} eq ''; if (exists $ENV{PERLIO} && $ENV{PERLIO} !~ /^(stdio|perlio|mmap)$/) { + # We are not prepared for anything else. print "1..0 # PERLIO='$ENV{PERLIO}' unknown\n"; exit 0; } @@ -27,6 +30,16 @@ SKIP: { sub check { my ($result, $expected, $id) = @_; + # An interesting dance follows where we try to make the following + # IO layer stack setups to compare equal: + # + # PERLIO UNIX-like DOS-like + # + # none or "" stdio unix crlf + # stdio stdio stdio + # perlio unix perlio unix perlio + # mmap unix mmap unix mmap + # if ($NONSTDIO) { # Get rid of "unix". shift @$result if $result->[0] eq "unix"; |