The following is not returning what I had expected...
SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/123};print "Yes - $a like
$homen" if $a =~ /^$home/;'
SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/ra};print "Yes - $a like
$homen" if $a =~ /^$home/;'
SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/ru};print "Yes - $a like
$homen" if $a =~ /^$home/;'
Yes - /var/run like /var/ru
I would have "assumed" that /var/run would NOT be "like" /var/ru just as
/var/run is not "like" /var/ra...
John W Moon
Full Version: regex problem
On Fri, 1 Jul 2005, Moon, John wrote:
| QUOTE |
| The following is not returning what I had expected... $a = q{/var/run}; $home = q{/var/ru}; print "Yes - $a like $homen" if $a =~ /^$home/; I would have "assumed" that /var/run would NOT be "like" /var/ru just as /var/run is not "like" /var/ra... |
It depends what you mean by "like".
In this case, the string in $home also appears as part of $a, so in that
sense there are "alike", and the code is doing the right thing.
If you want to verify that $a and $home are identical, it would be
easier to just check if one `eq` the other, as
print "Yes - $a like $homen" if $a eq $home;
That test will work if $home is '/var/run', but will fail on '/var/ru'.
--
Chris Devers
Moon, John [MJ], on Friday, July 1, 2005 at 11:30 (-0400 ) contributed
this to our collective wisdom:
MJ> I would have "assumed" that /var/run would NOT be "like" /var/ru just as
MJ> /var/run is not "like" /var/ra...
is "/var/ru" at the beginning of "/var/run" ? yes.
--
...m8s, cu l8r, Brano.
[If they get too annoying then we'll just have to get violent...]
this to our collective wisdom:
MJ> I would have "assumed" that /var/run would NOT be "like" /var/ru just as
MJ> /var/run is not "like" /var/ra...
is "/var/ru" at the beginning of "/var/run" ? yes.
--
...m8s, cu l8r, Brano.
[If they get too annoying then we'll just have to get violent...]
On 7/1/05, Moon, John <[Email Removed]> wrote:
| QUOTE |
| The following is not returning what I had expected... SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/123};print "Yes - $a like $homen" if $a =~ /^$home/;' SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/ra};print "Yes - $a like $homen" if $a =~ /^$home/;' SUN1-BATCH>perl -e '$a=q{/var/run}; $home=q{/var/ru};print "Yes - $a like $homen" if $a =~ /^$home/;' Yes - /var/run like /var/ru I would have "assumed" that /var/run would NOT be "like" /var/ru just as /var/run is not "like" /var/ra... John W Moon |
John
A regex match checks to see if the specified pattern appears in the
specified string. And the answer to the question "is /var/ru in
/var/run?" is "yes." Or to put it another way:
$a =~ /$home/
is functionally (although not proceedurally) equivalent to:
$a =~ /^.*$home.*$/
If you want to do a simple test for equality, use 'eq'. If you're
going to test for a pattern and want to match on the entire string,
anchor the patern at the beginning and end of the string:
$a =~ /^$home$/
but if $home is a simple string without regex metacharaters 'eq' it
going to be a lot faster than m//.
HTH,
-- jay
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