[bug-gawk] gawk4 split() function bug? or feature?

[Kent]

Hi there,

recently I found something strange about the split() function of gawk,
I am not sure if it is a bug, it would be good if you guys could
explain a bit. Thanks in advance.

my gawk version
kent$  gawk --version
GNU Awk 4.0.2

I know that the 3rd parameter of split() function is a regex. but take
a look these examples:

kent$  echo "foo.bar.baz" | awk '{split($0,a,"."); print "length of
a:" length(a);for (x in a) print a[x]}'
length of a:3
foo
bar
baz

split() looks "." as literature "dot", same as /[.]/ or /\./
but if I do:
kent$  echo "foo.bar.baz" | awk '{split($0,a,/./); print "length of
a:" length(a);for (x in a) print a[x]}'
length of a:12
(here we have 12 emplty lines)

then it worked as regex.

I thought that split() works only with regex constant , not dynamic
regex. however if I try this:
kent$  echo "foo.bar.baz" | awk '{split($0,a,"a."); print "length of
a:" length(a);for (x in a) print a[x]}'
length of a:3
foo.b
.b
(empty line here)

it DID work with dynamic regex and regex constant:

kent$  echo "foo.bar.baz" | awk '{split($0,a,/a./); print "length of
a:" length(a);for (x in a) print a[x]}'
length of a:3
foo.b
.b
(1 empty line)

I read the gawk manual, man page, info page also googled on inet,
cannot find the answer for split(str,array,".") question. Is it a bug?
can you explain me why this happened if it was not a bug?

Thank you!


Best Regards,

Kent