Removing lines containing same first string boundaries? topic

In article <lg7eo7kc$(E-Mail Removed)>, (E-Mail Removed) says...
>
> I have a plain text file with each line in the format:
>
> Start of line followed immediately by a string of character(s), a
> whitespace, another string, a newline.
>
> -------- file.txt -------
>
> SOMESTRING XXX
> SOMESTRING ZZZ
> SOMEOTHERSTRING YYYZZ23
> DIFFERENTSTRING HELLO
>
> -----------
>
> I would like to output each line that contains a string of a first
> character sequence but not repeat any line(s) with the same string as a
> first character sequence that appear further down the file. The output of
> running a perl procedure against the above file would then be:
>
> SOMESTRING XXX
> SOMEOTHERSTRING YYYZZ23
> DIFFERENTSTRING HELLO
>
> In other words, no repetition should occur of any first word boundary on
> each line in case the sequence happens to reappear on other line(s) as a
> first character boundary before each line's first whitespace.
>
> Alternatively, if given a parameter such as '^SOMESTRING' the output
> against the file would be narrowed down to:
>
> SOMESTRING XXX
>
> The second character string boundary (XXX) after the whitespace is
> arbitrary and should not affect the result but can be included in the
> output even if it happens to match SOMESTRING. So the output becomes the
> first occurence of ^SOMESTRING plus the remaining characters on the same
> line up until newline.
>
> Or if for example '^SOME' is passed as a parameter, the result would be:
>
> SOMESTRING XXX
> SOMEOTHERSTRING YYYZZ23
>
> In which ways can this be done efficiently in Perl?
>
> Many thanks for any ideas.
>
> Tuxedo

Just use a regex to match each line to your input parameter.

if ($line =~ /($param\w*)\s+.*/) { # If the first string matches input parameter
$string1 = ; # Extract string1 from the current line

if (grep {$string1 ne $_} @matched_array { # If string1 has not been seen before
print $line; # Print the line
push (@matched_array, $string1); # Put the string in the matched array
}
}

I have not tested this for errors but that is what I would start with. Not shown is the loop
to grab each line of the file into $line.

John Black