Having Trouble Removing a Newline from a Multiline String

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

Greetings Monks,

I am in need of your enlightment. I have a multiline string and sometimes it includes a blank newline, which I need to remove. I figured this was easy enough and thought this little subsitution regex would accomplish this: $vulns =~ s/^$//m; but no luck. I know my regex is matching, because if I use: $vulns =~ s/^$/-/m; it replaces that line with a dash.

Here is a sample string that I am trying to match:

5 Active Microsoft SQL Server 2000 Service Pack 4 Missing
5 Active Microsoft SQL Server Multiple Vulnerabilities
4 Active port 1433/tcp Microsoft SQL Server 2000 Latest Patch Not
4 Active port 3067/tcp Microsoft SQL Server 2000 Latest Patch Not

4 Active port 1723/tcp PPTP VPN Configuration Allows Weak MS-CHAPv1
[download]

Thanks,
Dru

Perl, the Leatherman of Programming languages. - qazwart

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Re: Having Trouble Removing a Newline from a Multiline String by ikegami (Patriarch) on Oct 02, 2008 at 06:57 UTC
`$` matches the point between `\n` and the character before it. `print "a\n\nc\n" =~ / a\n ^ $ c\n /mx ?1:0, "\n"; # 0 print "a\n\nc\n" =~ / a\n ^ $ \n c\n /mx ?1:0, "\n"; # 1` [download] Since `$` matches before the newline, it doesn't ever actually match the newline, and thus the newline is not getting substituted. What you want to do is remove newlines that start lines. `$_ = "abc\n" . "def\n" . "\n" . "jkl\n" . "\n" . "\n" . "stu\n"; s/^\n//mg; print;` [download] `abc def jkl stu` [download]	[reply] [d/l] [select]
Re^2: Having Trouble Removing a Newline from a Multiline String by Dru (Hermit) on Oct 02, 2008 at 07:11 UTC
That did the trick, thank you. Thanks, Dru Perl, the Leatherman of Programming languages. - qazwart	[reply]
Re: Having Trouble Removing a Newline from a Multiline String by BrowserUk (Patriarch) on Oct 02, 2008 at 06:39 UTC
You're matching the blank line, but not the newline you're trying to remove. Use `s/\n^$//mg`. (/g in case there is more than one.) Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re: Having Trouble Removing a Newline from a Multiline String by jwkrahn (Abbot) on Oct 02, 2008 at 11:01 UTC
Another way to do what you want: `$vulns =~ tr/\n//s;` [download]	[reply] [d/l]


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