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perlfaq6 example is wrong: pull out lines between two patterns #8553

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p5pRT opened this issue Aug 5, 2006 · 5 comments
Closed

perlfaq6 example is wrong: pull out lines between two patterns #8553

p5pRT opened this issue Aug 5, 2006 · 5 comments
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distro-mswin32 documentation

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@p5pRT
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p5pRT commented Aug 5, 2006

Migrated from rt.perl.org#40084 (status was 'resolved')

Searchable as RT40084$
@p5pRT
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p5pRT commented Aug 5, 2006

From @Corion

Created by Administrator@dawn

The example in perlfaq6 is wrong for the question "How can I pull
out lines between two patterns that are themselves on
different lines?"​:

  while (<>) {
  $in_header = 1 .. /^$/;
  $in_body = /^$/ .. eof();
  # now choose between them
  } continue {
  reset if eof(); # fix $.
  }

1) The comment '#fix $.' is wrong. C&lt;reset;&gt; doesn't touch $.
2) The line number does not get reset.
3) The matching does not stop at EOF and start fresh with
the next file, because C<reset;> doesn't reset the flipflop
operators. Most likely this example was using m?^$? previously
but was modified without rechecking.

I have no better suggestion to fix this than to use m??, even
though this makes this example an example of how to use two
arcana that are seldom used and/or shouldn't be used at all.

-max

Perl Info 

Flags:
     category=core
     severity=low

Site configuration information for perl v5.8.5:

Configured by Administrator at Fri Aug  6 13:59:28 2004.

Summary of my perl5 (revision 5 version 8 subversion 5) configuration:
   Platform:
     osname=MSWin32, osvers=4.0, archname=MSWin32-x86-multi-thread
     uname=''
     config_args='undef'
     hint=recommended, useposix=true, d_sigaction=undef
     usethreads=undef use5005threads=undef 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='cl', ccflags ='-nologo -GF -W3 -MD -Zi -DNDEBUG -O1 -DWIN32 
-D_CONSOLE -DNO_STRICT -DHAVE_DES_FCRYPT  -DPERL_IMPLICIT_CONTEXT 
-DPERL_IMPLICIT_SYS -DUSE_PERLIO -DPERL_MSVCRT_READFIX',
     optimize='-MD -Zi -DNDEBUG -O1',
     cppflags='-DWIN32'
     ccversion='', gccversion='', gccosandvers=''
     intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
     d_longlong=undef, longlongsize=8, d_longdbl=define, longdblsize=10
     ivtype='long', ivsize=4, nvtype='double', nvsize=8, 
Off_t='__int64', lseeksize=8
     alignbytes=8, prototype=define
   Linker and Libraries:
     ld='link', ldflags ='-nologo -nodefaultlib -debug -opt:ref,icf 
-libpath:"c:\perl\5.8.5\lib\CORE"  -machine:x86'
     libpth="C:\Programme\Microsoft Visual C++ Toolkit 2003\lib"
     libs=  oldnames.lib kernel32.lib user32.lib gdi32.lib winspool.lib 
  comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib 
netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib  version.lib 
odbc32.lib odbccp32.lib msvcrt.lib
     perllibs=  oldnames.lib kernel32.lib user32.lib gdi32.lib 
winspool.lib  comdlg32.lib advapi32.lib shell32.lib ole32.lib 
oleaut32.lib  netapi32.lib uuid.lib wsock32.lib mpr.lib winmm.lib 
version.lib odbc32.lib odbccp32.lib msvcrt.lib
     libc=msvcrt.lib, so=dll, useshrplib=yes, libperl=perl58.lib
     gnulibc_version='undef'
   Dynamic Linking:
     dlsrc=dl_win32.xs, dlext=dll, d_dlsymun=undef, ccdlflags=' '
     cccdlflags=' ', lddlflags='-dll -nologo -nodefaultlib -debug 
-opt:ref,icf  -libpath:"c:\perl\5.8.5\lib\CORE"  -machine:x86'

Locally applied patches:



@INC for perl v5.8.5:
     c:/perl/5.8.5/lib
     c:/perl/site/5.8.5/lib
     .


Environment for perl v5.8.5:
     HOME (unset)
     LANG (unset)
     LANGUAGE (unset)
     LD_LIBRARY_PATH (unset)
     LOGDIR (unset)
     PATH=C:\Programme\Microsoft Visual C++ Toolkit 
2003\bin;C:\Programme\Microsoft Visual Studio .NET 
2003\Vc7\bin;C:\WINNT\Microsoft.NET\Framework\v1.1.4322;C:\Programme\Microsoft 
IntelliType 
Pro\;C:\texmf\miktex\bin;C:\WINNT\system32;C:\WINNT;C:\WINNT\System32\Wbem;c:\perl\5.8.5\bin;C:\Programme\Microsoft 
SDK\Bin\.;C:\Programme\Microsoft SDK\Bin\WinNT\.;C:\Programme\Microsoft 
SDK\Bin\.;C:\Programme\Microsoft SDK\Bin\WinNT\.;C:\Programme\Microsoft 
Visual C++ Toolkit 2003\bin;C:\Programme\Subversion\bin;c:\perl\5.8.5\bin
     PERL_BADLANG (unset)
     SHELL (unset)

@p5pRT
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p5pRT commented Aug 17, 2006

From rick@bort.ca

On Sat, Aug 05, 2006 at 02​:57​:48PM -0700, Max Maischein wrote​:

The example in perlfaq6 is wrong for the question "How can I pull
out lines between two patterns that are themselves on
different lines?"​:

 while \(\<>\) \{
     $in\_header =   1  \.\. /^$/;
     $in\_body   = /^$/ \.\. eof\(\);
\# now choose between them
 \} continue \{
reset if eof\(\);        \# fix $\.
 \}

1) The comment '#fix $.' is wrong. C&lt;reset;&gt; doesn't touch $.
2) The line number does not get reset.
3) The matching does not stop at EOF and start fresh with
the next file, because C<reset;> doesn't reset the flipflop
operators. Most likely this example was using m?^$? previously
but was modified without rechecking.

I have no better suggestion to fix this than to use m??, even
though this makes this example an example of how to use two
arcana that are seldom used and/or shouldn't be used at all.

Maybe the following? I'm guessing the example is meant to deal with
maildir-style mailboxes?

  while (<>) {
  $in_header = 1 .. /^$/;
  $in_body = /^$/ .. eof;
  # now choose between them
  } continue {
  $. = 0 if eof; # reset $.
  }

The eof() in the original isn't right either because it will only be
true for the last file read. To test each file in @​ARGV you need to use
eof, without parentheses.

--
Rick Delaney
rick@​bort.ca

@p5pRT
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p5pRT commented Aug 17, 2006

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

@p5pRT
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p5pRT commented Sep 13, 2006

From @rgarcia

On 11/08/06, Rick Delaney <rick@​bort.ca> wrote​:

Maybe the following? I'm guessing the example is meant to deal with
maildir-style mailboxes?

 while \(\<>\) \{
     $in\_header =   1  \.\. /^$/;
     $in\_body   = /^$/ \.\. eof;
     \# now choose between them
 \} continue \{
     $\. = 0 if eof;         \# reset $\.
 \}

The eof() in the original isn't right either because it will only be
true for the last file read. To test each file in @​ARGV you need to use
eof, without parentheses.

I changed perlfaq6 accordingly in the perlfaq svn repository (revision 7831).

@p5pRT
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p5pRT commented May 12, 2008

p5p@spam.wizbit.be - Status changed from 'open' to 'resolved'

@p5pRT p5pRT closed this as completed May 12, 2008
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