So far we have been getting our input data from awk's main
input stream—either the standard input (usually your terminal, sometimes
the output from another program) or from the
files specified on the command line. The awk language has a
special built-in command called
can be used to read input under your explicit control.
getline command is used in several different ways and should
not be used by beginners.
The examples that follow the explanation of the
include material that has not been covered yet. Therefore, come back
and study the
getline command after you have reviewed the
rest of this Web page and have a good knowledge of how awk works.
getline command returns one if it finds a record and zero if
it encounters the end of the file. If there is some error in getting
a record, such as a file that cannot be opened, then
returns −1. In this case, gawk sets the variable
ERRNO to a string describing the error that occurred.
In the following examples, command stands for a string value that represents a shell command.
NOTE: When --sandbox is specified (see Options), reading lines from files, pipes and coprocesses is disabled.