How can I add characters at the beginning and end of every non-empty line in Perl?

Question

I would like to use this:

perl -pi -e 's/^(.*)$/\"$1\",/g' /path/to/your/file

for adding " at beginning of line and ", at end of each line in text file. The problem is that some lines are just empty lines and I don't want these to be altered. Any ideas how to modify above code or maybe do it completely differently?

Answer 1

perl -pi -e 's/^(.+)$/\"$1\",/g' /your/file

.* matches 0 or more characters; .+ matches 1 or more.

You may also want to replace the .+ with .*\S.* to ensure that only lines containing a non-whitespace character are quoted.

Answer 2

change .* to .+

In other words lines must contain at 1 or more characters. .* represents zero or more characters.

Answer 3

You should be able to just replace the * (0 or more) with a + (1 or more), like so:

perl -pi -e 's/^(.+)$/\"$1\",/g' /path/to/your/file

Answer 4

sed -r 's/(.+)/"\1"/' /path/to/your/file

Answer 5

all you are doing is adding something to the front and back of the line, so there is no need for regex. Just print them out. Regex for such a task is expensive if your file is big.

gawk

$ awk 'NF{print "\042" $0 "\042,"}' file

or Perl

$ perl -ne 'chomp;print "\042$_\042,\n" if ($_ ne "") ' file

Answer 6

Others have already answered the regex syntax issue, let's look at that style.

s/^(.*)$/\"$1\",/g

This regex suffers from "leaning toothpick syndrome" where /\/\/ makes your brain bleed.

s{^ (.+) $}{ "$1", }x;

Use of balanced delimiters, the /x modifier to space things out and elimination of unnecessary backwhacks makes the regex far easier to read. Also the /g is unnecessary as this regex is only ever going to match once per line.