Regular Expressions 101

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/
(?sm)interface (\S*)(?:(?!^!$).)*port-security.*?!$
/
gm
(?sm)
match the remainder of the pattern with the following effective flags: gms
s modifier: single line. Dot matches newline characters
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
interface
matches the characters interface literally (case sensitive)
1st Capturing Group
(\S*)
\S
matches any non-whitespace character (equivalent to [^\r\n\t\f\v ])
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group
(?:(?!^!$).)*
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
Negative Lookahead
(?!^!$)
Assert that the Regex below does not match
^ asserts position at start of a line
! matches the character ! with index 3310 (2116 or 418) literally (case sensitive)
$ asserts position at the end of a line
. matches any character
port-security
matches the characters port-security literally (case sensitive)
.
matches any character
*? matches the previous token between zero and unlimited times, as few times as possible, expanding as needed (lazy)
! matches the character ! with index 3310 (2116 or 418) literally (case sensitive)
$ asserts position at the end of a line
Global pattern flags
g modifier: global. All matches (don't return after first match)
m modifier: multi line. Causes ^ and $ to match the begin/end of each line (not only begin/end of string)
Your regular expression does not match the subject string.Try launching the debugger to find out why.

Regular Expression
No Match

/
/
gm

Test String

Code Generator

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Generated Code

Loading code sample...
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report.
For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html

Regular Expressions 101

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