What does a { at the end of a Perl one-liner mean?
perl
Solution
From the Perl help:
-n assume "while (<>) { ... }" loop around program
This is purely a textual operation, so it gives this program:
while (<>) { $_{$F[0]}+=$F[1]}print"$_ $_{$_}"for keys%_;{ }
This is an abuse of the `-n` switch because the while loop is closed early due to the unmatched `}` in the original program. But the closing `}` that is added by the `-n` switch still needs to match with something, and that's why there needs to be an extra `{` at the end of the program, even though it doesn't do anything.
In other words, the only reason the last `{` is there is to not give a syntax error.
Problem
I've seen this one-liner ``` perl -lane '$_{$F[0]}+=$F[1]}print"$_ $_{$_}"for keys%_;{' file ``` here: How can I sum values in column based on the value in another column? and I don't remember how the "{" at the end works. Could someone explain how it works?