Why do I get a blank line while substituting a string with '%>' in Perl?

Question

This is the input text:

<title>Company Selection</title>
<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />

and I want to substitute the CSS reference with two lines:

<%@ include file="../common/cmufx.jsp" %>
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbpSA_css.jsp" />

Here's the Perl statement:

while(<>){
    s{<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />}{
--><%@ include file="../common/cmufx.jsp" %> 
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbpSA_css.jsp" />;};
print;
}

And in output I get:

<title>Company Selection</title>

-->
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbpSA_css.jsp" />

• If I remove the '%>' element at the end of the first substituting line, I get the line to be printed.
• If the substituting line ends with '% >', it gets printed.
• If I escape the %, the line does not get printed

---

The whole source of my script:

#!/usr/bin/perl

use strict;
use warnings;


while(<>){
    s{<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />}{
--><%@ include file="../common/cmufx.jsp" %>
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbpSA_css.jsp" />;};

    s{<link rel="stylesheet" type="text/css" href="../css/style_hbp_css.jsp" />}{
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbp_css.jsp" />};

    s{<%@ include file="../common/cmufx.jsp" %>}{};

    s{../img/banner.jpg}{<%=basePath%>/<fmt:message key="application.version"/>/img/banner.jpg};

    print;
}

Answer 1

It just dawned on me, you are viewing the results through a web server aren't you? The <% %> stuff should be replaced by a template program or server side includes. You will never see that text. Most likely the file ../common/cmufx.jsp does not exist (e.g. the path is wrong) or it contains nothing. Take a look at what the program spits out on the commandline. If it is what you are expecting then the problem is somewhere else (e.g. the path to cmufx.jsp or your ssi not being setup right).

Your data has a space where your regex has a /:

data                                               V
<link rel="stylesheet" type="text/css" href="../css style_hbpSA_css.jsp" />
regex                                              V
<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />

Also, you are using . in your regex without escaping them. The . character in a regex matches any character other than a newline (unless the /s option is used). Your regex should probably look like

s{<link rel="stylesheet" type="text/css" href="\.\./css style_hbpSA_css\.jsp" />}{}

or

s{<link rel="stylesheet" type="text/css" href="[.][.]/css style_hbpSA_css[.]jsp" />}{}

depending on which looks less ugly to you. The first escapes the special meaning of ., and the second creates a character class of one character, the ..

You say you are still having problems, here is a full script that does the right thing, can you tell us where your code diverges from this:

#!/usr/bin/perl

use strict;
use warnings;

while(<DATA>){
s{<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />}{
<%@ include file="../common/cmufx.jsp" %> 
<link rel="stylesheet" type="text/css" href="<%=basePath%>/<fmt:message key="application.version"/>/css/style_hbpSA_css.jsp" />;};
print;
}

__DATA__
<title>Company Selection</title>
<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />

Answer 2

Firstly, I strongly recommend against using regular expressions to manipulate HTML. Use something like HTML::Tree.

Nonetheless, when I tried your code, it worked. The only thing I changed was what I assume was a typo: your input included:

href="../css style_hbpSA_css.jsp"

Your pattern was:

href="../css/style_hbpSA_css.jsp"

I assume you wanted both to be the same (although it would be even better to have '..' in the pattern).

One thing I would check for is weird (that is, Windows) line endings in your input file.

Answer 3

The answer is that after that substitution, I was ALSO requesting

s{<%@ include file="../common/cmufx.jsp" %>}{};

therefore the line got deleted.

sorry for trashing your time and I do thank you for all the answers.

Answer 4

It's because you have a new line after {

s{<link rel="stylesheet" type="text/css" href="../css/style_hbpSA_css.jsp" />}{ #your new line is here
<%@ include file="../common/cmufx.jsp" %>