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(gawk.info)Other Arguments

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Other Command-Line Arguments
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   Any additional arguments on the command-line are normally treated as
input files to be processed in the order specified.   However, an
argument that has the form `VAR=VALUE', assigns the value VALUE to the
variable VAR--it does not specify a file at all.  (This was discussed
earlier in Note: Assigning Variables on the Command Line.
)

   All these arguments are made available to your `awk' program in the
`ARGV' array (Note: Built-in Variables).  Command-line options and
the program text (if present) are omitted from `ARGV'.  All other
arguments, including variable assignments, are included.   As each
element of `ARGV' is processed, `gawk' sets the variable `ARGIND' to
the index in `ARGV' of the current element.

   The distinction between file name arguments and variable-assignment
arguments is made when `awk' is about to open the next input file.  At
that point in execution, it checks the file name to see whether it is
really a variable assignment; if so, `awk' sets the variable instead of
reading a file.

   Therefore, the variables actually receive the given values after all
previously specified files have been read.  In particular, the values of
variables assigned in this fashion are _not_ available inside a `BEGIN'
rule (Note: The `BEGIN' and `END' Special Patterns.),
because such rules are run before `awk' begins scanning the argument
list.

   The variable values given on the command-line are processed for
escape sequences (Note: Escape Sequences).  (d.c.)

   In some earlier implementations of `awk', when a variable assignment
occurred before any file names, the assignment would happen _before_
the `BEGIN' rule was executed.  `awk''s behavior was thus inconsistent;
some command-line assignments were available inside the `BEGIN' rule,
while others were not.  Unfortunately, some applications came to depend
upon this "feature."  When `awk' was changed to be more consistent, the
`-v' option was added to accommodate applications that depended upon
the old behavior.

   The variable assignment feature is most useful for assigning to
variables such as `RS', `OFS', and `ORS', which control input and
output formats before scanning the data files.  It is also useful for
controlling state if multiple passes are needed over a data file.  For
example:

     awk 'pass == 1  { PASS 1 STUFF }
          pass == 2  { PASS 2 STUFF }' pass=1 mydata pass=2 mydata

   Given the variable assignment feature, the `-F' option for setting
the value of `FS' is not strictly necessary.  It remains for historical
compatibility.