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(m4.info)M4wrap

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Saving input
============

   It is possible to `save' some text until the end of the normal input
has been seen.  Text can be saved, to be read again by `m4' when the
normal input has been exhausted.  This feature is normally used to
initiate cleanup actions before normal exit, e.g., deleting temporary
files.

   To save input text, use the builtin `m4wrap':

     m4wrap(STRING, ...)

which stores STRING and the rest of the arguments in a safe place, to
be reread when end of input is reached.

     define(`cleanup', `This is the `cleanup' actions.
     ')
     =>
     m4wrap(`cleanup')
     =>
     This is the first and last normal input line.
     =>This is the first and last normal input line.
     ^D
     =>This is the cleanup actions.

   The saved input is only reread when the end of normal input is seen,
and not if `m4exit' is used to exit `m4'.

   It is safe to call `m4wrap' from saved text, but then the order in
which the saved text is reread is undefined.  If `m4wrap' is not used
recursively, the saved pieces of text are reread in the opposite order
in which they were saved (LIFO--last in, first out).