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Points About getline to Remember

Here are some miscellaneous points about getline that you should bear in mind:

• When getline changes the value of $0 and NF, @command{awk} does not automatically jump to the start of the program and start testing the new record against every pattern. However, the new record is tested against any subsequent rules.
• Many @command{awk} implementations limit the number of pipelines that an @command{awk} program may have open to just one. In @command{gawk}, there is no such limit. You can open as many pipelines (and coprocesses) as the underlying operating system permits.
• An interesting side effect occurs if you use getline without a redirection inside a BEGIN rule. Because an unredirected getline reads from the command-line data files, the first getline command causes @command{awk} to set the value of FILENAME. Normally, FILENAME does not have a value inside BEGIN rules, because you have not yet started to process the command-line data files. (d.c.) (See section The BEGIN and END Special Patterns, also see section Built-in Variables That Convey Information.)

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