substr and strings on the outside

JPaul has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: substr and strings on the outside by OeufMayo (Curate) on Aug 19, 2001 at 20:23 UTC
Hello, I'm not sure I perfectly understood what you wanted to do. Do you want to append '12345' to the `$f` variable, with at least 5 spaces at the beginning? If so, here's a snippet that should do what you want: `sub pad { my ($spaces, $string) = @_; return( " " x (5 - length $spaces) . $string ); } my $add = "12345"; my $f = " " x 4; # for leading spaces smaller than 5 print "[" . pad( $f, '12345') . "]";` [download] <kbd>-- my $OeufMayo = new PerlMonger::Paris({http => 'paris.mongueurs.net'});</kbd>	[reply] [d/l]
Re: substr and strings on the outside by George_Sherston (Vicar) on Aug 19, 2001 at 20:29 UTC
I'm not sure this does what you want in all cases, but it might be a step forward: `my $f = " "; substr($f, length $f, length $f, "12345");` [download] Or do you want the new string to go in at exactly position 5, even if the old string is shorter than that? Then: `my $f = " "; my $l = length $f; substr($f, $l, $l, " " x ($l<5 ? 5-$l : 0) . "12345");` [download] Having said that, this all may betray my failure to understand the question, since one could get the same result with `$f . " " x ($l<5 ? 5-$l : 0) . "12345"`. § George Sherston	[reply] [d/l] [select]
(elbie): substr and strings on the outside by elbie (Curate) on Aug 19, 2001 at 20:20 UTC
Regex search and replace: `my $f = " "; $f =~ s/^(.{0,5}).{0,5}/${1}12345/;` [download] The only problem is this regex doesn't pad extra spaces if your string is too short, but at least it still does the replacement. elbieelbieelbie	[reply] [d/l]
Re: substr and strings on the outside by synapse0 (Pilgrim) on Aug 20, 2001 at 01:52 UTC
I'm not sure I fully understand what you are trying to do.. but maybe sprintf might help you. -Syn0	[reply]
Re: substr and strings on the outside by JPaul (Hermit) on Aug 20, 2001 at 02:10 UTC
My apologies for being vague, Imagine a billing statement in text form. There are a number of lines, generally all different lengths before the \n, which I need to alter. For example, a line may be (literally): `Joe Bloggs, 1615 Thislane Street\n` [download] Now imagine I need to replace the address with a piece of text that is longer than the one in the original text - thusly my `substr($f, 20, 30, "This is a new longer address\n");` [download] will have substr complain 'substr outside string'. What I want perl to do is say "Okay, its longer than the original string was, thats fine, I don't really care. Honest." Hopefully this is clearer JP -- Alexander Widdlemouse undid his bellybutton and his bum dropped off --	[reply] [d/l] [select]
Re: Re: substr and strings on the outside by scott (Chaplain) on Aug 20, 2001 at 02:45 UTC
This works fine for me: `use strict; use warnings; my $f= " Joe Bloggs, 1615 Thislane Street\n"; substr($f, 20, 12345, "This is a new longer address\n"); print $f;` [download] `substr` has no problems making the string longer. It's inserting new bytes where the first new byte is beyond the end of the original scalar that causes errors. So the following fails with the error message you mention: `substr($f, length($f) + 10, 12345, "This is a new longer address\n");` [download]	[reply] [d/l] [select]
Re: substr and strings on the outside by mandog (Curate) on Aug 20, 2001 at 07:05 UTC
I suspect I don't understand the question (or Perl) but... If you are trying to insert an arbitary string wouldn't s/// do the trick? `use strict; use warnings; my $f="Joe Bloggs, 1615 Thislane Street, MyTown, NZ, 1851\n"; my $in=" This is a new longer address"; print $f; $f=~s/,.*/,$in/s; print $f;` [download] --mandog	[reply] [d/l]