getline [varhairsp;] [< file] command | getline [var]
The first form reads input from file or the next file on the command line, and the second form reads the output of command. 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 is parsed into fields, setting NF, NR, and FNR. If var is specified, the result is assigned to var, and neither $0 nor NF is changed. Thus, if the result is assigned to a variable, the current line does not change. getline is actually a function, and it returns 1 if it reads a record successfully, 0 at EOF, and -1 if for some reason it is unsuccessful.