Originally posted golang/go#79835, but was informed I should post this here.
The x flag instructs the parser to ignore most whitespace, unless it is backslashed or within brackets. It's useful for breaking up long patterns into readable parts. Additionally, the x flag allows comments within the pattern, starting with a #
For example:
# multiline.pl
s/
# A comment
lang
|
pher
/!/x
echo "Golang" | perl -p multiline.pl # Go!
echo "Gopher" | perl -p multiline.pl # Go!
More details: https://perldoc.perl.org/perlre#/x-and-/xx
I haven't found any duplicate issues, but I did find #3 (comment), which says that x is arguably unnecessary.
There are certainly workarounds for breaking up a regular expression into multiple lines without the x flag. In Go terms, one could use strings.Join on an array of strings, for example, and it would also be pretty simple to clean up the strings to remove comments and ignored spaces.
In my personal use case, when a regular expression gets significantly complicated, I like to move it to its own file, and use go:embed (or the equivalent in another language). This helps avoid clutter in the code file IMO, and allows one to focus on the code logic. I believe that the x flag helps support this use case.
To my knowledge, x is currently supported in Perl, Ruby, and Rust.
Thanks!
Originally posted golang/go#79835, but was informed I should post this here.
The
xflag instructs the parser to ignore most whitespace, unless it is backslashed or within brackets. It's useful for breaking up long patterns into readable parts. Additionally, thexflag allows comments within the pattern, starting with a#For example:
More details: https://perldoc.perl.org/perlre#/x-and-/xx
I haven't found any duplicate issues, but I did find #3 (comment), which says that
xis arguably unnecessary.There are certainly workarounds for breaking up a regular expression into multiple lines without the
xflag. In Go terms, one could usestrings.Joinon an array of strings, for example, and it would also be pretty simple to clean up the strings to remove comments and ignored spaces.In my personal use case, when a regular expression gets significantly complicated, I like to move it to its own file, and use
go:embed(or the equivalent in another language). This helps avoid clutter in the code file IMO, and allows one to focus on the code logic. I believe that thexflag helps support this use case.To my knowledge,
xis currently supported in Perl, Ruby, and Rust.Thanks!