Hello,
gnu grep -C allows for output in context to the matched line
is there an updated way to do this in perl using $. == $linenumber +
context?
I looked into the other thread that mentioned it, but none of the
scripts worked.
I tried the -00 switch and regex backreferences with $1, etc but
thought there must be an easier way.
more importantly,
Is there a way to use such a match as the replacement pattern for a
different line?
Ideally the substitution would be like:
$. == $matchedLineNumber +/- $contextNumber and s/$patternInMatched/
$newPattern/ and print $_;
Here's an example:
I want to edit specific lines in a file using an array of the specific
line numbers.
But I don't know how to reference an element of the array when I use
an implicit loop of the lines in the file from the -p or -n switch.
print line numbers and lines of the file, test.txt
$ perl -wnl -e 'print "$. $_";' test.txt
1 animal cat
2 tag this line
3 animal dog
4 tag this line
5 animal cat
6 tag this line
7
I want to substitute a string in the lines with 'tag' with the
replacement string from the previous line something like:
long way
# get the line numbers of the lines you want the substitution to occur
$ perl -wnl -e '/tag/ and print "$. $_";' test.txt
2 tag this line
4 tag this line
6 tag this line
#then code a substitution line for each line; manually looking at
previous line
#!/usr/bin/env perl -i.old -wpl
$. == 2 and s/this line/cat animal/;
$. == 4 and s/this line/dog animal/;
$. == 6 and s/this line/cat animal/;
instead I want to use an array and loop over the lines in the file
rather than line by line, but
if <STDIN> is in the implicit array from the -p switch, how do I
reference it?
#!/usr/bin/env perl -i.old -wpl
@array = (2,4,6)
$. = $array[what goes here?] and s/this line/cat animal/
I also tried
#!/usr/bin/env perl -i.old -wpl
@array = (2,4,6)
while (<>){
$. = $array[what goes here?] and s/this line/cat animal/
}
it will work if I specify one line at a time as an argument and I know
beforehand that the line in context is +1 from the matched line:
#!/usr/bin/env perl -s -i.old -wpl
# beforehand find all line numbers that have the pattern
BEGIN {
$ln or warn "Enter line: $0 -ln\n" and exit 255
}
# sample nearby -1 lines that need substitution @lines =
(7303,7309,7315,7321,7327,7333,7339,7345,7351,7357,7363,7369,7375,7381,7387,7393,7399,7405,7411,7417,7423,7429,7435,7441,7447,7453,7459,7465,7471,7477,7483,7489,7495,7501,7507,7513,7519,7525,7531);
$. == $ln + 1 and s/this line/$pattern/g;
Any thoughts or suggestions appreciated!
Best,
tony
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