Read next line of input. Original awk does not support the syntax
to open multiple input streams.
The first form reads input from
and the second form reads the output of
Both forms read one line at a time, and each time
the statement is executed it gets the next line
of input. The line of input is assigned to $0
and it is parsed into fields, setting NF,
NR and FNR.
var is specified, the result is assigned
var and the $0 is not changed. Thus, if
the result is assigned to a variable, the
current line does not change.
It is actually a function and it returns 1 if it
reads a record successfully, 0 if end-of-line is
encountered, and -1 if for some reason it is