язык сканирования и обработки шаблонов (pattern scanning and processing language)
Стандартный ввод (Stdin)
The standard input shall be used only if no file operands are
specified, or if a file operand is '-', or if a progfile option-
argument is '-'; see the INPUT FILES section. If the awk program
contains no actions and no patterns, but is otherwise a valid awk
program, standard input and any file operands shall not be read
and awk shall exit with a return status of zero.
