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Reading Input Files

   In the typical `awk' program, all input is read either from the
standard input (by default the keyboard, but often a pipe from another
command) or from files whose names you specify on the `awk' command
line.  If you specify input files, `awk' reads them in order, reading
all the data from one before going on to the next.  The name of the
current input file can be found in the built-in variable `FILENAME'
(see Built-in Variables.).

   The input is read in units called records, and processed by the
rules one record at a time.  By default, each record is one line.  Each
record is split automatically into fields, to make it more convenient
for a rule to work on its parts.

   On rare occasions you will need to use the `getline' command, which
can do explicit input from any number of files (*note Explicit Input
with `getline': Getline.).


Controlling how data is split into records.
An introduction to fields.
Non-Constant Fields
Non-constant Field Numbers.
Changing Fields
Changing the Contents of a Field.
Field Separators
The field separator and how to change it.
Constant Size
Reading constant width data.
Multiple Line
Reading multi-line records.
Reading files under explicit program control using the `getline' function.
Close Input
Closing an input file (so you can read from the beginning once more).