in reply to simulating bash

I saw your post on the perl-beginners list, but deleted it, so I was hoping someone else would reply and I could work off that, so I'm glad you posted it here, too.

Here's my take: 

# parse variable assignments out of the file
while ($ebuildcontents =~ /\b([-A-Z0-9_]+)=\"(.*?)\"{1}?/sgc) {
  $ebuildvars{$1} = $2;
}

[download]
I'm curious about your \"{1}? part there. Are quotes optional? I'd need to see how the config file is formatted, to help you extract these variables appropriately. But let's move onto the troublesome part: 
foreach (keys %ebuildvars) {
  $ebuildvars{$_} =~ s/\$\{?([-A-Z0-9_]+)\}?/$ebuildvars{$1}/gs;
}

[download]
The problem is that if VAR1 = "say $VAR2" and VAR2 = "hi $VAR3" and VAR3 = "jeff", you want to be able to expand ALL of these, so you get VAR1 = "say hi jeff", VAR2 = "hi jeff", and VAR3 = "jeff", right?

If so, let me know, and I'll help you write a solution. It's kind of related to a dependency tree...

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

Replies are listed 'Best First'.
Re: Re: simulating bash
by agaffney (Beadle) on May 13, 2004 at 15:21 UTC
    Well, the '\"{1}?' part was my attempt to make the match non-greedy. Although, I think the '(.+?)' right before it accomplishes that. I just never removed it.

    Quote: 
    The problem is that if VAR1 = "say $VAR2" and VAR2 = "hi $VAR3"
and VAR3 = "jeff", you want to be able to expand ALL of these,
so you get VAR1 = "say hi jeff", VAR2 = "hi jeff", and
VAR3 = "jeff", right?

    That's exactly what I want to do.
[reply]
      Ok, then. Here's a code block that demonstrates how to do it by using a dependency structure: 
      #!/usr/bin/perl

use strict;
use warnings;

my %vars;
my %depend;

while (<DATA>) {
  chomp;
  if (/^\s*(\w+)\s*=\s*(?:"([^"]*)"|(.*))/) {
    my ($name, $val) = ($1, $+);
    $vars{$name} = $val;
    $depend{$name} = [ $vars{$name} =~ /\$(\w+)/g ];
  }
}

expand(\%vars, \%depend);

sub expand {
  my ($varhash, $dephash, $queue) = @_;

  $queue ||= [ keys %$varhash ];

  # for each item in the queue
  for (@$queue) {

    # make sure its dependencies are expanded
    expand($varhash, $dephash, $dephash->{$_});

    # then interpolate the variables in this item
    $varhash->{$_} =~ s/\$(\w+)/$varhash->{$1}/g;
  }
}

use Data::Dumper;
print Dumper(\%vars);

__DATA__
VAR1 = "say $VAR2"
VAR2 = "hi $VAR3"
VAR3 = jeff

      [download]
      You can see I parse my variables a little differently. If it's more complex for you, then so be it, but I used simple cases. I used the $+ variable because I want to match the string INSIDE quotes (not the quotes themselves) or else an un-quoted string, and I don't know which of these matches, so $+ gives me the last matching capture group. It's like writing defined($2) ? $2 : $3 in this case, but I didn't want to do that.

      You can see how expand() looks similar to the post-order traversal code I showed you a day or two ago. It's a similar concept. The function, when called with only the two hashrefs, uses the keys of the %vars hash as its queue. Each recursive call uses the dependent variables of the current one as its queue. I hope it's understandable.

      _____________________________________________________
      Jeff[japhy]Pinyan: Perl, regex, and perl hacker, who'd like a job (NYC-area)
      s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;
[reply]
[d/l]
[select]
        I modified your code slightly to incorporate in my program.

        sub expand_bash_var {
  my ($varhash, $dephash, $queue) = @_;

  $queue ||= [ keys %$varhash ];

  # for each item in the queue
  for (@$queue) {

    # make sure its dependencies are expanded
    expand_bash_var($varhash, $dephash, $dephash->{$_});

    # then interpolate the variables in this item
    $varhash->{$_} =~ s/\$\{?(\w+)\}?/$varhash->{$1}/g;
  }
}

sub get_depend {
  my $ebuildfname = shift;
  my $ebuildcontents;
  my %ebuildvars;
  my $pkgname = $ebuildfname;
  my %vardepend;

#  print "Getting depend for '$ebuildfname'\n";
  $pkgname =~ s|/usr/portage/||;
  $pkgname =~ s|(.+)/.+/(.+).ebuild|$1/$2|;
  my $pkg = parse_package_name($pkgname);
  $pkg->{version} =~ s/^-//;
  $ebuildvars{PV} = "$pkg->{version}$pkg->{suffix}";

  open EBUILD, "< $ebuildfname" or die "Couldn't open '$ebuildfname' t
+o get DEPEND\n";
  while(<EBUILD>) {
    $ebuildcontents .= $_;
  }
  close EBUILD;

  while($ebuildcontents =~ /\b([-A-Z0-9_]+)\s*=\s*\"(.*?)\"/sgc) {
    $ebuildvars{$1} = $2;
  }
  print "Calling expand_bash_var() for '$ebuildfname'\n";
  expand_bash_var(\%ebuildvars, \%vardepend);
  print "Done with expand_bash_var() for '$ebuildfname'\n";

  my $depend = $ebuildvars{'DEPEND'} || '';
  $depend .= " $ebuildvars{'RDEPEND'}" if(defined $ebuildvars{'RDEPEND
+'});
  $depend =~ s/(\s+|\n+)/ /gs;
  print "$depend\n";

  return $depend;
}

        [download]

        which gives me the output:

        Deep recursion on subroutine "main::expand_bash_var" at ./portage.pl line 124.

        The file it is processing contains:

        RESTRICT="nostrip"
IUSE="3dfx sse mmx 3dnow xml2 truetype nls cjk doc ipv6 debug static p
+am sdk bindist"

filter-flags "-funroll-loops"

ALLOWED_FLAGS="-fstack-protector -march -mcpu -O -O1 -O2 -O3 -pipe"
strip-flags

if [ "${ARCH}" = "x86" ]
then
    if [ -z "${SYNAPTICS}" ]
    then
        SYNAPTICS="yes"
    fi
else
    unset SYNAPTICS
fi

USE_SNAPSHOT="no"

PATCH_VER="2.1.25.4"
FT2_VER="2.1.3"
XCUR_VER="0.3.1"
SISDRV_VER="311003-1"
SAVDRV_VER="1.1.27t"
MGADRV_VER="1_3_0beta"
VIADRV_VER="0.1"
SYNDRV_VER="0.12.0"

BASE_PV="${PV}"
MY_SV="${BASE_PV//\.}"
S="${WORKDIR}/xc"
SYNDIR="${WORKDIR}/synaptics"
SRC_PATH="mirror://xfree/${BASE_PV}/source"
HOMEPAGE="http://www.xfree.org"

X_PATCHES="http://dev.gentoo.org/~spyderous/xfree/patchsets/${PV}/XFre
+e86-${PV}-patches-${PATCH_VER}.tar.bz2
    http://www.cpbotha.net/files/dri_resume/xfree86-dri-resume-v8.patc
+h"

X_DRIVERS="http://people.mandrakesoft.com/~flepied/projects/wacom/xf86
+Wacom.c.gz
    http://www.probo.com/timr/savage-${SAVDRV_VER}.zip
    http://www.winischhofer.net/sis/sis_drv_src_${SISDRV_VER}.tar.gz
    http://w1.894.telia.com/~u89404340/touchpad/files/synaptics-${SYND
+RV_VER}.tar.bz2"
MS_COREFONTS="./andale32.exe ./arial32.exe
    ./arialb32.exe ./comic32.exe
    ./courie32.exe ./georgi32.exe
    ./impact32.exe ./times32.exe
    ./trebuc32.exe ./verdan32.exe
    ./webdin32.exe"
MS_FONT_URLS="${MS_COREFONTS//\.\//mirror://sourceforge/corefonts/}"

SRC_URI="${SRC_PATH}/X${MY_SV}src-1.tgz
    ${SRC_PATH}/X${MY_SV}src-2.tgz
    ${SRC_PATH}/X${MY_SV}src-3.tgz
    ${SRC_PATH}/X${MY_SV}src-4.tgz
    ${SRC_PATH}/X${MY_SV}src-5.tgz
    doc? ( ${SRC_PATH}/X${MY_SV}src-6.tgz
        ${SRC_PATH}/X${MY_SV}src-7.tgz )"

SRC_URI="${SRC_URI}
    ${X_PATCHES}
    ${X_DRIVERS}
    nls? ( mirror://gentoo/gemini-koi8-u.tar.bz2 )
    mirror://gentoo/eurofonts-X11.tar.bz2
    mirror://gentoo/xfsft-encodings.tar.bz2
    mirror://gentoo/XFree86-compose.dir-0.1.bz2
    mirror://gentoo/XFree86-en_US.UTF-8.old.bz2
    mirror://gentoo/XFree86-locale.alias.bz2
    mirror://gentoo/XFree86-locale.dir.bz2
    mirror://gentoo/gentoo-cursors-tad-${XCUR_VER}.tar.bz2
    truetype? ( !bindist? ( ${MS_FONT_URLS} ) )"

LICENSE="Adobe-X CID DEC DEC-2 IBM-X NVIDIA-X NetBSD SGI UCB-LBL XC-2
    bigelow-holmes-urw-gmbh-luxi christopher-g-demetriou national-semi
+conductor
    nokia tektronix the-open-group todd-c-miller x-truetype xfree86-1.
+0
    MIT SGI-B BSD FTL | GPL-2 MSttfEULA"
SLOT="0"
KEYWORDS="x86 ppc sparc alpha mips hppa amd64 ia64"

DEPEND=">=sys-apps/baselayout-1.8.3
    >=sys-apps/portage-2.0.50_pre9
    >=sys-libs/ncurses-5.1
    >=sys-libs/zlib-1.1.3-r2
    >=sys-devel/flex-2.5.4a-r5
    >=dev-libs/expat-1.95.3
    >=media-libs/freetype-${FT2_VER}-r2
    >=media-libs/fontconfig-2.1-r1
    >=x11-base/opengl-update-1.4
    >=x11-misc/ttmkfdir-3.0.4
    >=sys-apps/sed-4
    >=sys-devel/patch-2.5.9
    sys-apps/util-linux
    dev-lang/perl
    media-libs/libpng
    app-arch/unzip
    pam? ( >=sys-libs/pam-0.75 )
    truetype? ( !bindist? ( app-arch/cabextract ) )
    !virtual/x11
    !x11-libs/xft"

PDEPEND="x86? ( 3dfx? ( >=media-libs/glide-v3-3.10 ) )"

PROVIDE="virtual/x11
    virtual/opengl
    virtual/glu
    virtual/xft"

DESCRIPTION="XFree86: free X server"

PATCH_DIR=${WORKDIR}/patch

        [download]
[reply]
[d/l]
[select]
        That is pretty cool. I assume this is far faster than trying to pass the values through bash and reading the output back in.
[reply]

In Section Seekers of Perl Wisdom