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(gawk.info)Getline/Variable/Pipe

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Using `getline' into a Variable from a Pipe
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   When you use `COMMAND | getline VAR', the output of COMMAND is sent
through a pipe to `getline' and into the variable VAR.  For example, the
following program reads the current date and time into the variable
`current_time', using the `date' utility, and then prints it:

     BEGIN {
          "date" | getline current_time
          close("date")
          print "Report printed on " current_time
     }

   In this version of `getline', none of the built-in variables are
changed and the record is not split into fields.

   According to POSIX, `EXPRESSION | getline VAR' is ambiguous if
EXPRESSION contains unparenthesized operators other than `$'; for
example, `"echo " "date" | getline VAR' is ambiguous because the
concatenation operator is not parenthesized. You should write it as
`("echo " "date") | getline VAR' if you want your program to be
portable to other `awk' implementations.  (It happens that `gawk' gets
it right, but you should not rely on this. Parentheses make it easier
to read, anyway.)