File: gawk.info,  Node: Retrying Input,  Next: Command-line directories,  Prev: Read Timeout,  Up: Reading Files

4.12 Retrying Reads After Certain Input Errors
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This minor node describes a feature that is specific to 'gawk'.

   When 'gawk' encounters an error while reading input, by default
'getline' returns -1, and subsequent attempts to read from that file
result in an end-of-file indication.  However, you may optionally
instruct 'gawk' to allow I/O to be retried when certain errors are
encountered by setting a special element in the 'PROCINFO' array (*note
Auto-set::):

     PROCINFO["INPUT_NAME", "RETRY"] = 1

   When this element exists, 'gawk' checks the value of the system (C
language) 'errno' variable when an I/O error occurs.  If 'errno'
indicates a subsequent I/O attempt may succeed, 'getline' instead
returns -2 and further calls to 'getline' may succeed.  This applies to
the 'errno' values 'EAGAIN', 'EWOULDBLOCK', 'EINTR', or 'ETIMEDOUT'.

   This feature is useful in conjunction with 'PROCINFO["INPUT_NAME",
"READ_TIMEOUT"]' or situations where a file descriptor has been
configured to behave in a non-blocking fashion.