(gawk.info.gz) Getline Notes

Info Catalog

(gawk.info.gz) Getline/Variable/Coprocess

(gawk.info.gz) Getline

(gawk.info.gz) Getline Summary

 
 3.8.9 Points to Remember About `getline'
 ----------------------------------------
 
 Here are some miscellaneous points about `getline' that you should bear
 in mind:
 
    * When `getline' changes the value of `$0' and `NF', `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 `awk' implementations limit the number of pipelines that an
      `awk' program may have open to just one.  In `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 `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.)  ( BEGIN/END, also  Auto-set.)
 
    * Using `FILENAME' with `getline' (`getline < FILENAME') is likely
      to be a source for confusion.  `awk' opens a separate input stream
      from the current input file.  However, by not using a variable,
      `$0' and `NR' are still updated.  If you're doing this, it's
      probably by accident, and you should reconsider what it is you're
      trying to accomplish.
 

Info Catalog

(gawk.info.gz) Getline/Variable/Coprocess

(gawk.info.gz) Getline

(gawk.info.gz) Getline Summary