| CC: | bug-perlfaq [...] rt.cpan.org, perl5-porters [...] perl.org |
| Subject: | [perl #108712] documentation bug in perlfaq5 (To delete lines, ...) |
| Date: | Sat, 21 Jan 2012 10:54:30 -0800 |
| To: | "OtherRecipients of perl Ticket #108712":; |
| From: | "Father Chrysostomos via RT" <perlbug-followup [...] perl.org> |
Thank you for your report.
The perl faq are now maintained separately on CPAN, so I’m forwarding
your message to the CPAN ticket.
On Sat Jan 21 08:14:05 2012, sdziegie@stronglg.demon.co.uk wrote:
Show quoted text
>
> This is a bug report for perl from sdziegie@stronglg.demon.co.uk,
> generated with the help of perlbug 1.39 running under perl 5.12.1.
>
> Hello,
>
> I think that I have found a bug in the perlfaq5 documentation, namely
> the
> text:
>
> To delete lines, only print the ones that you want.
>
> perl -ni -e 'print unless /d/' inFile.txt
>
> ... or ...
>
> perl -pi -e 'next unless /d/' inFile.txt
>
> I think that the first method using -ni should read:
>
> perl -ni -e 'print if /d/' inFile.txt
>
> I do not think that the second method can ever work and should be
> removed
> from the documentation altogether. Reading the 3rd edition of the
> Camel
> Book it states that the -p switch has an implied:
>
> continue {
> print or die "-p destination: $!\n";
> }
>
> at the end. I believe that the 'next' can never bypass this continue
> block and
> hence the example will always print every line.
>
> Here is how I tested this out:
>
> cat > inFile.txt.orig << EOT
> This should stay
> this goes
> as should this
> bye
> keep dis
> bye
> EOT
>
> # Method 1 as per perlfaq5 (I believe the documentation is wrong)
> cp inFile.txt.orig inFile.txt; perl -ni -e 'print unless /d/'
> inFile.txt; cat inFile.txt
>
> # Proposed documentation fix for Method 1 (see above)
> cp inFile.txt.orig inFile.txt; perl -ni -e 'print if /d/' inFile.txt;
> cat inFile.txt
>
> # Method 2 as per perlfaq5 (I believe that this should be struck from
> the
> # documentation altogether as it cannot delete anything)
> cp inFile.txt.orig inFile.txt; perl -pi -e 'unless /d/' inFile.txt;
> cat inFile.txt
> ---
> Flags:
> category=docs
> severity=low
> ---
> This perlbug was built using Perl 5.12.1 - Fri May 6 13:30:46 UTC
> 2011
> It is being executed now by Perl 5.12.1 - Fri May 6 13:25:31 UTC
> 2011.
>
> Site configuration information for perl 5.12.1:
>
> Configured by abuild at Fri May 6 13:25:31 UTC 2011.
>
> Summary of my perl5 (revision 5 version 12 subversion 1)
> configuration:
>
> Platform:
> osname=linux, osvers=2.6.32, archname=i586-linux-thread-multi
> uname='linux build34 2.6.32 #1 smp 2011-02-21 10:34:10 +0100 i686
> athlon i386 gnulinux '
> config_args='-ds -e -Dprefix=/usr -Dvendorprefix=/usr
> -Dinstallusrbinperl -Dusethreads -Di_db -Di_dbm -Di_ndbm -Di_gdbm
> -Duseshrplib=true -Doptimize=-fomit-frame-pointer
> -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector
> -funwind-tables -fasynchronous-unwind-tables -g -Wall -pipe
> -Accflags=-DPERL_USE_SAFE_PUTENV'
> hint=recommended, useposix=true, d_sigaction=define
> useithreads=define, usemultiplicity=define
> useperlio=define, d_sfio=undef, uselargefiles=define,
> usesocks=undef
> use64bitint=undef, use64bitall=undef, uselongdouble=undef
> usemymalloc=n, bincompat5005=undef
> Compiler:
> cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE
> -DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe
> -fstack-protector -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
> optimize='-fomit-frame-pointer -fmessage-length=0 -O2 -Wall
> -D_FORTIFY_SOURCE=2 -fstack-protector -funwind-tables
> -fasynchronous-unwind-tables -g -Wall -pipe',
> cppflags='-D_REENTRANT -D_GNU_SOURCE -DPERL_USE_SAFE_PUTENV
> -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector'
> ccversion='', gccversion='4.5.0 20100604 [gcc-4_5-branch revision
> 160292]', gccosandvers=''
> intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
> d_longlong=define, longlongsize=8, d_longdbl=define,
> longdblsize=12
> ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t',
> lseeksize=8
> alignbytes=4, prototype=define
> Linker and Libraries:
> ld='cc', ldflags =' -fstack-protector'
> libpth=/lib /usr/lib /usr/local/lib
> libs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
> perllibs=-lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
> libc=/lib/libc-2.11.2.so, so=so, useshrplib=true,
> libperl=libperl.so
> gnulibc_version='2.11.2'
> Dynamic Linking:
> dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E
> -Wl,-rpath,/usr/lib/perl5/5.12.1/i586-linux-thread-multi/CORE'
> cccdlflags='-fPIC', lddlflags='-shared -fomit-frame-pointer
> -fmessage-length=0 -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector
> -funwind-tables -fasynchronous-unwind-tables -g -Wall -pipe'
>
> Locally applied patches:
>
>
> ---
> @INC for perl 5.12.1:
> /usr/lib/perl5/site_perl/5.12.1/i586-linux-thread-multi
> /usr/lib/perl5/site_perl/5.12.1
> /usr/lib/perl5/vendor_perl/5.12.1/i586-linux-thread-multi
> /usr/lib/perl5/vendor_perl/5.12.1
> /usr/lib/perl5/5.12.1/i586-linux-thread-multi
> /usr/lib/perl5/5.12.1
> .
>
> ---
> Environment for perl 5.12.1:
> HOME=/home/sdziegie
> LANG=en_GB.UTF-8
> LANGUAGE (unset)
> LC_COLLATE=POSIX
> LD_LIBRARY_PATH=/usr/local/lib:/opt/experimental/lib:/usr/X11R6/lib:
> LOGDIR (unset)
>
PATH=/home/sdziegie/bin:/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/X11R6/bin:/usr/games:/opt/kde3/bin:/usr/lib/mit/bin:/usr/lib/mit/sbin:/opt/gnome/bin:/usr/lib/qt3/bin:/usr/lib/festival:/usr/local/apache-
Show quoted text> maven-2.0.9/bin:/usr/lib/festival:/usr/local/apache-maven-2.0.9/bin
> PERL_BADLANG (unset)
> SHELL=/bin/bash
--
Father Chrysostomos
---
via perlbug: queue: perl5 status: new
https://rt.perl.org:443/rt3/Ticket/Display.html?id=108712