This section describes a feature that is specific to gawk.
When gawk encounters an error while reading input, by
default getline returns −1, and subsequent attempts to
read from that file result in an end-of-file indication. However, you
may optionally instruct gawk to allow I/O to be retried when
certain errors are encountered by setting a special element in
the PROCINFO array (see Built-in Variables That Convey Information):
PROCINFO["input_name", "RETRY"] = 1
When this element exists, gawk checks the value of the system
(C language)
errno variable when an I/O error occurs. If errno indicates
a subsequent I/O attempt may succeed, getline instead returns
−2 and
further calls to getline may succeed. This applies to the errno
values EAGAIN, EWOULDBLOCK, EINTR, or ETIMEDOUT.
This feature is useful in conjunction with
PROCINFO["input_name", "READ_TIMEOUT"] or situations where a file
descriptor has been configured to behave in a non-blocking fashion.