This bug affects my Lubuntu 17.10 (64-bit) system, which has version 5.26.0-8ubuntu1 of the perl and perl-doc packages. I noticed the bug immediately upon checking for it after Zanna (https://launchpad.net /~rose-anna-bleasdale / https://askubuntu.com/users/527764/zanna) reported experiencing it in Ubuntu MATE 17.10. Until this bug is fixed, I suggest the workaround of setting the PAGER environment variable to "less" so that the proper configuration for less is used; other full workarounds are also effective (see below).
The problem does not appear to depend in any way on what sort of terminal emulator is used. I tried in LXTerminal (TERM=xterm), XTerm (TERM=xterm), a virtual console (TERM=linux), and via SSH (TERM=xterm). Zanna tried in MATE Terminal (TERM=xterm), GNOME Terminal (TERM=xterm- 256color), Konsole (TERM=xterm-256color), Tilda (TERM=xterm-256color), XTerm (TERM=xterm), and a virtual console (TERM=linux). See https://chat.stackexchange.com/transcript/message/42130009#42130009 and subsequent messages for details. It occurred for us both no matter what terminals we used. I believe this is the same bug as reported here. In case it is helpful, I have attached a file showing the debugging output produced by running "perldoc -D perlsyn" on my Lubuntu 17.10 system. Note the presence of this line: About to call Pod::Perldoc::ToTerm->pager_configuration("/usr/bin /sensible-pager") I suspect that the problem is that the necessary configuration for less to permit terminal escape sequences--specifically, that the -R option either be passed to it or present in the LESS environment variable--is not satisfied when the pager configuration for sensible-pager is used, even when sensible-pager runs less, as it does by default in Ubuntu. I further suspect that many, or perhaps all, 17.10 systems have this bug in their default configuration (though it would only be noticed if users install and run perldoc). This strongly resembles https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735134. This bug may be considered a regression, in that the problem had previously occurred and was then prevented by the addition of this code in Perldoc.pm, which is present in 16.04 but removed in 17.10 (see below for details): # fix visible escape codes in ToTerm output # https://bugs.debian.org/758689 local $ENV{LESS} = defined $ENV{LESS} ? "$ENV{LESS} -R" : "-R"; The simplest workaround for this bug that I am aware of is to pass the -t flag to perldoc. As in the workaround described in the bug report here, the resulting formatting is readable but not as fancy as usual. A *full* workaround is also possible, and is only slightly more complicated. Telling perldoc explicitly that you want "less" by defining the PAGER environment variable works: PAGER=less perldoc perlsyn Otherwise, it finds sensible-pager first (see above), and appears not to place -R in LESS (see below), because it does not know that the sensible-pager shell script runs less. The problem may also be avoided by ensuring that an environment variable with the name LESS and a value that specifies the R option is present. For example, this works: LESS=-R perldoc perlsyn Or this may be preferred, because if you have a LESS environment variable with other options, they will still be used (and if not, it has the same effect as above): LESS="$LESS -R" perldoc perlsyn Or you can pipe to less and pass -R: perldoc perlsyn | less -R If these workarounds do not work for you (i.e., for the original author of this bug report), then I might be mistaken in my belief that the bug I am experiencing is the same as yours. This bug does not appear to affect Ubuntu 16.04 LTS. It does not happen on my Lubuntu 16.04 LTS (64-bit) system. Ubuntu 16.04 LTS has "/usr/share/perl/5.22/Pod/Perldoc.pm" which uses this loop to open the document in a pager: foreach my $pager (@pagers) { $self->aside("About to try calling $pager $output\n"); if ($self->is_vms) { last if system("$pager $output") == 0; } else { # fix visible escape codes in ToTerm output # bugs.debian.org/758689 local $ENV{LESS} = defined $ENV{LESS} ? "$ENV{LESS} -R" : "-R"; last if system("$pager \"$output\"") == 0; } } Ubuntu 17.10 has this corresponding loop, which no longer directly attempts to modify the LESS environment variable in order to prevent Debian Bug 758689 from occurring: foreach my $pager (@pagers) { $self->aside("About to try calling $pager $output\n"); if ($self->is_vms) { last if system("$pager $output") == 0; } elsif($self->is_amigaos) { last if system($pager, $output) == 0; } else { my $formatter = $self->{'formatter_class'}; if ( $formatter->can('pager_configuration') ) { $self->aside("About to call $formatter" . "->pager_configuration(\"$pager\")\n"); $formatter->pager_configuration($pager, $self); } last if system("$pager \"$output\"") == 0; } } ** Bug watch added: Debian Bug tracker #735134 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=735134 ** Bug watch added: Debian Bug tracker #758689 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=758689 ** Attachment added: "Text displayed in the terminal when I ran "perldoc -D perlsyn"" https://bugs.launchpad.net/ubuntu/+source/perl/+bug/1734702/+attachment/5032746/+files/perldoc_-D_perlsyn.txt -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to perl in Ubuntu. https://bugs.launchpad.net/bugs/1734702 Title: perldoc shows lots of escapes Status in perl package in Ubuntu: Confirmed Bug description: Fresh konsole: $ echo $TERM xterm-256color $ type perldoc perldoc is /usr/bin/perldoc $ dpkg -S /usr/bin/perldoc diversion by perl-doc from: /usr/bin/perldoc diversion by perl-doc to: /usr/bin/perldoc.stub perl, perl-doc: /usr/bin/perldoc $ echo $PAGER $ perldoc perlsyn (Now in pager:) ESC[1mNAMEESC[0m perlsyn - Perl syntax ESC[1mDESCRIPTIONESC[0m A Perl program consists of a sequence of declarations and statements which ... That's a lot of ESCapes. PAGER=more gets me "2NAME2" and the like. $ locate perlsyn /usr/share/man/man1/perlsyn.1.gz /usr/share/man/man1/perlsynology.1.gz /usr/share/perl/5.26.0/pod/perlsyn.pod /usr/share/perl/5.26.0/pod/perlsynology.pod No cached files apparently. This works reasonably: TERM=none perldoc perlsyn | (TERM=vt100 less) - but looses the bolds etc. This works well: man perlsyn This also works as expected, showing bolds and stuff, but I find it impractical: perldoc perlsyn | cat So perldoc applies terminal appropriate escapes where it should not? ProblemType: Bug DistroRelease: Ubuntu 17.10 Package: perl-doc 5.26.0-8ubuntu1 ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8 Uname: Linux 4.13.0-17-generic x86_64 ApportVersion: 2.20.7-0ubuntu3.5 Architecture: amd64 CurrentDesktop: KDE Date: Mon Nov 27 15:23:57 2017 EcryptfsInUse: Yes InstallationDate: Installed on 2017-07-18 (132 days ago) InstallationMedia: Kubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412) PackageArchitecture: all SourcePackage: perl UpgradeStatus: Upgraded to artful on 2017-11-27 (0 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/perl/+bug/1734702/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
