05-16-2012
Quote:
Originally Posted by
neutronscott
when I have to use eval I usually single quote everything except what I specifically want evaluated prior.
This is correct, but in this case the single quotes are doing the same as the escaping backslashes: they prevent everything inside from being evaluated at the first pass - including the double quotes, which lose their special meaning to the shell when inside the single quotes.
You can watch this effect when using several numbers of eval's on the same line (which is - save for demonstration - of course of no practical value although syntactically correct). Correct escaping with several backslashes will manage even this tricky predicament, while single quotes will get interpreted away like double quotes do.
I hope this helps.
bakunin
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LEARN ABOUT SUSE
text::parsewords
Text::ParseWords(3pm) Perl Programmers Reference Guide Text::ParseWords(3pm)
NAME
Text::ParseWords - parse text into an array of tokens or array of arrays
SYNOPSIS
use Text::ParseWords;
@lists = nested_quotewords($delim, $keep, @lines);
@words = quotewords($delim, $keep, @lines);
@words = shellwords(@lines);
@words = parse_line($delim, $keep, $line);
@words = old_shellwords(@lines); # DEPRECATED!
DESCRIPTION
The &nested_quotewords() and "ewords() functions accept a delimiter (which can be a regular expression) and a list of lines and then
breaks those lines up into a list of words ignoring delimiters that appear inside quotes. "ewords() returns all of the tokens in a
single long list, while &nested_quotewords() returns a list of token lists corresponding to the elements of @lines. &parse_line() does
tokenizing on a single string. The &*quotewords() functions simply call &parse_line(), so if you're only splitting one line you can call
&parse_line() directly and save a function call.
The $keep argument is a boolean flag. If true, then the tokens are split on the specified delimiter, but all other characters (quotes,
backslashes, etc.) are kept in the tokens. If $keep is false then the &*quotewords() functions remove all quotes and backslashes that are
not themselves backslash-escaped or inside of single quotes (i.e., "ewords() tries to interpret these characters just like the Bourne
shell). NB: these semantics are significantly different from the original version of this module shipped with Perl 5.000 through 5.004.
As an additional feature, $keep may be the keyword "delimiters" which causes the functions to preserve the delimiters in each string as
tokens in the token lists, in addition to preserving quote and backslash characters.
&shellwords() is written as a special case of "ewords(), and it does token parsing with whitespace as a delimiter-- similar to most
Unix shells.
EXAMPLES
The sample program:
use Text::ParseWords;
@words = quotewords('s+', 0, q{this is "a test" of quotewords "for you});
$i = 0;
foreach (@words) {
print "$i: <$_>
";
$i++;
}
produces:
0: <this>
1: <is>
2: <a test>
3: <of quotewords>
4: <"for>
5: <you>
demonstrating:
0 a simple word
1 multiple spaces are skipped because of our $delim
2 use of quotes to include a space in a word
3 use of a backslash to include a space in a word
4 use of a backslash to remove the special meaning of a double-quote
5 another simple word (note the lack of effect of the backslashed double-quote)
Replacing "quotewords('s+', 0, q{this is...})" with "shellwords(q{this is...})" is a simpler way to accomplish the same thing.
AUTHORS
Maintainer: Alexandr Ciornii <alexchornyATgmail.com>.
Previous maintainer: Hal Pomeranz <pomeranz@netcom.com>, 1994-1997 (Original author unknown). Much of the code for &parse_line()
(including the primary regexp) from Joerk Behrends <jbehrends@multimediaproduzenten.de>.
Examples section another documentation provided by John Heidemann <johnh@ISI.EDU>
Bug reports, patches, and nagging provided by lots of folks-- thanks everybody! Special thanks to Michael Schwern <schwern@envirolink.org>
for assuring me that a &nested_quotewords() would be useful, and to Jeff Friedl <jfriedl@yahoo-inc.com> for telling me not to worry about
error-checking (sort of-- you had to be there).
perl v5.12.1 2010-04-26 Text::ParseWords(3pm)