Arguments with quotations(" ") to be not escaped

Question

I am writing a Perl script which enables the addition and modification of parameters maintained in a particular file. The script takes the following arguments; Parameter name($paraName), Parameter value($paraVal) and the file ($profile). The script checks if the parameter($paraName) exists already. if it does, it just changes the value($paraVal) else adds both the parameter($paraName) and the value($paraVal) to the file($profile).

Following is the block of code for the same:

   print "  checking if parameter is already avaialable";
   my $response = system("egrep -qs  \"$paraName =\" $profile");
   $rc = 1;
   if ($response == 0) {
    print "  Parameter is already available, changing the value now! ";
    $rc = system("sed -i 's:.*$paraName.*:$paraName = $paraVal \# Parameter changed by $script:' $profile");
    print "   Parameter $paraName has been updated with the value $paraVal in the Profile successfully \n\n";
   }
   else{
    print "  Parameter is not available, Adding the Paremeter now! ";
    $rc = system("echo \"$paraName = $paraVal \# Parameter added by $script\" >> $profile");
    print "   Parameter $paraName has been added with the value $paraVal in the Profile successfully \n\n";
   }

The script works fine for most cases, except when I have arguments with double quotes to be added as a new parameter. It works file for hash(#), slashes (), etc, when passes within a single quote(' ').

This is working in case of changing the value($paraVal) when the parameter($paraName) already exists. But while a new parameter has to be added, this fails to add double quotes in the parameter name.

Would appreciate some help here.

Answer 1

Here is an example of how you could write it as pure Perl:

use feature qw(say);
use strict;
use warnings;

my ( $paraName, $paraVal, $profile ) = @ARGV;
my $script = $0;

open ( my $fh, '<', $profile ) or die "Could not open file '$profile': $!";
my $found = 0;
while( my $line = <$fh> ) {
    chomp $line;
    if ( my ($key) = $line =~ /^(\Q$paraName\E)\s*=\s*/) {
        say "$key = $paraVal \# Parameter changed by $script";
        $found = 1;
    }
    else {
        say $line;
    }
}
close $fh;
if ( !$found ) {
    say "$paraName = $paraVal \# Parameter added by $script";
}

Edit:

The above script does not modify the profile file, but instead writes the modified file to standard output. So it was meant to be used together with Shell redirection to save the output to a new file. To modify the profile file directly, you could use:

use feature qw(say);
use strict;
use warnings;

die "Bad arguments!" if @ARGV != 3;
my ( $paraName, $paraVal, $profile ) = @ARGV;
my $script = $0;
@ARGV = ( $profile );
$^I = '.bak';
my $found = 0;
while (my $line = <<>>) {
    chomp $line;
    if ( my ($key) = $line =~ /^(\Q$paraName\E)\s*=\s*/) {
        say "$key = $paraVal \# Parameter changed by $script";
        $found = 1;
    }
    else {
        say $line;
    }
} continue {
    say "$paraName = $paraVal \# Parameter added by $script" if eof && !$found;
}

This will first save the original profile file to a backup file with .bak extension, and then overwrite the profile file with the modified content.

Answer 2

Try following code as alternative

#!/usr/bin/perl

use strict;
use warnings;
use feature 'say';

use Pod::Usage;
use Getopt::Long;
use Data::Dumper;

my %opt;        # program options
my %param;      # parameters storage
my $fh;         # file handle

GetOptions (
                'file|f=s'      => \$opt{file},
                'name|n=s'      => \$opt{name},
                'value|v=s'     => \$opt{value},
                'operation|o=s' => \$opt{op},
                'help|h'        => \$opt{help},
                'man|m'         => \$opt{man},
                'debug|d'       => \$opt{debug}
            ) or pod2usage(1);

pod2usage(1) if $opt{help};
pod2usage(-exitval => 0, -versose => 2) if $opt{man};

pod2usage(1) unless $opt{file};

open $fh, "< $opt{file}"
        or die "Couldn't open $opt{file}";

my @lines = <$fh>;

close $fh;

chomp @lines;

print Dumper(\@lines) if $opt{debug};

push @lines, "$opt{name} = $opt{value}"
            if $opt{op} eq 'add';

@lines = map { /$opt{name}\s*=/ ? '' : $_ } @lines
            if $opt{op} eq 'del';

@lines = map {
    s/($opt{name})\s*=\s*(.*)/$1 = $opt{value}/; $_
} @lines    if $opt{op} eq 'mod';

map{ say } @lines
            if $opt{op} eq 'view';

map {
    /$opt{name}\s*=\s*(.*)/ and say 'Verify: '
    . ($1 eq $opt{value} ? 'ok' : 'no')
} @lines    if $opt{op} eq 'check';

my %save = map { $_ => 1 } qw/add del mod/;

print Dumper(\@lines) if $opt{debug};

if( $save{ $opt{op} } ) {
    open $fh, "> $opt{file}"
            or die "Couldn't open $opt{file}";

    map { say $fh $_ } @lines;

    close $fh;
}

__END__

=head1 NAME

program - modify configuration file

=head1 SYNOPSIS

program [options] [file ...]

 Usage:
    program -op [add|del|mod|view|check] -n param -v value -f file
 Options:
    --file,-f       configuration filename
    --name,-n       parameter name
    --value,-v      parameter value
    --operation,-o  operation to perform
    --help,-h       brief help message
    --man,-m        full documentation
    --debug,-d      debug mode

=head1 OPTIONS

=over 8

=item B<--file,-f>

Configuration file to edit

=item B<--name,-n>

Configuration parameter name to operate on

=item B<--value,-v>

Configuration parameter value to operate on

=item B<--operation,-o>

Operation to perform on parameter: add, del, mod, view, check

=item B<--debug,-d>

Debug flag to print debug messages.

=item B<--help,-h>

Print a brief help message and exits.

=item B<--man,-m>

Prints the manual page and exits.

=back

=head1 DESCRIPTION

B<This program> allows to operate on configuation files variables.

=head1 AUTHOR

B<Polar Bear> L<https://stackoverflow.com/users/12313309/polar-bear>

=cut