(gawk.info.gz) Nextfile Statement

 
 Using `gawk''s `nextfile' Statement
 -----------------------------------
 
    `gawk' provides the `nextfile' statement, which is similar to the
 `next' statement.  However, instead of abandoning processing of the
 current record, the `nextfile' statement instructs `gawk' to stop
 processing the current data file.
 
    The `nextfile' statement is a `gawk' extension.  In most other `awk'
 implementations, or if `gawk' is in compatibility mode (
 Command-Line Options Options.), `nextfile' is not special.
 
    Upon execution of the `nextfile' statement, `FILENAME' is updated to
 the name of the next data file listed on the command line, `FNR' is
 reset to one, `ARGIND' is incremented, and processing starts over with
 the first rule in the program.  (`ARGIND' hasn't been introduced yet.
  Built-in Variables.)  If the `nextfile' statement causes the
 end of the input to be reached, then the code in any `END' rules is
 executed.   The `BEGIN' and `END' Special Patterns BEGIN/END.
 
    The `nextfile' statement is useful when there are many data files to
 process but it isn't necessary to process every record in every file.
 Normally, in order to move on to the next data file, a program has to
 continue scanning the unwanted records.  The `nextfile' statement
 accomplishes this much more efficiently.
 
    While one might think that `close(FILENAME)' would accomplish the
 same as `nextfile', this isn't true.  `close' is reserved for closing
 files, pipes, and coprocesses that are opened with redirections.  It is
 not related to the main processing that `awk' does with the files
 listed in `ARGV'.
 
    If it's necessary to use an `awk' version that doesn't support
 `nextfile', see  Implementing `nextfile' as a Function Nextfile
 Function, for a user-defined function that simulates the `nextfile'
 statement.
 
    The current version of the Bell Laboratories `awk' ( Other
 Freely Available `awk' Implementations Other Versions.)  also supports
 `nextfile'.  However, it doesn't allow the `nextfile' statement inside
 function bodies ( User-Defined Functions User-defined.).  `gawk'
 does; a `nextfile' inside a function body reads the next record and
 starts processing it with the first rule in the program, just as any
 other `nextfile' statement.
 
    *Caution:*  Versions of `gawk' prior to 3.0 used two words (`next
 file') for the `nextfile' statement.  In version 3.0, this was changed
 to one word, because the treatment of `file' was inconsistent. When it
 appeared after `next', `file' was a keyword; otherwise, it was a
 regular identifier.  The old usage is no longer accepted; `next file'
 generates a syntax error.
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(gawk.info.gz) Next Statement
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