Shell Programming and Scripting

I wish to check if my file has a line that does not start with '#' and has
1. Listen and 2. 443

Code:

 echo "Listen               443" > test.out

grep 'Listen *443' test.out | grep -v '#'
Listen               443

The above worked fine but when the entry changes to the below the grep fails when i dont want it to fail.

Code:

echo "Listen     192.888.22.111:443" > test.out

Also, i do grep -v '#' to ignore lines having # i.e comments but is there a way to check if # is the starting (not necessary the first character considering there are whitespaces before the #) charecter in the line only then it should be ignored else be considered by the grep query.

So....

should not be considered

But

should be considered.

Would this do?

Code:

grep  '^[^#]*Listen.*[^0-9]443\([^0-9]\|$\)' file

The problem is that your expression is matching Listen followed by any number of spaces then 443. Your definition is explicit in being for 'any number of spaces' with the * sequence.

Do you really mean "Match records that start with Listen and end with :443 #" ? That would be grep "^Listen.*:443 #$" or you could be more explicit and say that it would have to match an IP address structure with "^Listen.*([0-9]{1,3}\.){3}[0-9]{1,3}:443 #$"


To explain a little more:-

Code:

^                             - Start of line
Listen                        - Liternal text, exactly as it is.
.*                            - zero or more of any character
([0-9]{1,3}\.){3}             - exactly 3 of the bracketed bit (see line below and sub-note below)
[0-9]{1,3}                    - between 1 & 3 characters between 0 and 9 inclusive
:443 #                        - Literal text, exactly as it is.
$                             - End of line, important to avoid false matches that don't end at the end of your search..

So to expand more on ([0-9]{1,3}\.){3} the braces {3} mean three of the previous thing. In this case the thing is ([0-9]{1,3}\.) which is between 1 & 3 digits followed by an explicit dot/full stop. You have to use \. because the dot is special as you have in the .* which means any number of any character.

If the line might not start with Listen then you might just want to exclude a leading #, so you end up with the more complicated "^[^#]Listen.*([0-9]{1,3}\.){3}[0-9]{1,3}:443 #$" which is "Do not start with a hash. The [^#] means "Not this/these character(s)" which might be a bit confusing given it follows a ^ marking the start of the line. Of course if this might not be the first character, you might want to drop the first ^ anchoring it to the start of the line.




Does that help, or have I just confused things?

Robin