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(m4.info)Format

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Formatted output
================

   Formatted output can be made with `format':

     format(FORMAT-STRING, ...)

which works much like the C function `printf'.  The first argument is a
format string, which can contain `%' specifications, and the expansion
of `format' is the formatted string.

   Its use is best described by a few examples:

     define(`foo', `The brown fox jumped over the lazy dog')
     =>
     format(`The string "%s" is %d characters long', foo, len(foo))
     =>The string "The brown fox jumped over the lazy dog" is 38 characters long

   Using the `forloop' macro defined in Note: Loops, this example
shows how `format' can be used to produce tabular output.

     forloop(`i', 1, 10, `format(`%6d squared is %10d
     ', i, eval(i**2))')
     =>     1 squared is	    1
     =>     2 squared is	    4
     =>     3 squared is	    9
     =>     4 squared is	   16
     =>     5 squared is	   25
     =>     6 squared is	   36
     =>     7 squared is	   49
     =>     8 squared is	   64
     =>     9 squared is	   81
     =>    10 squared is	  100

   The builtin `format' is modeled after the ANSI C `printf' function,
and supports the normal `%' specifiers: `c', `s', `d', `o', `x', `X',
`u', `e', `E' and `f'; it supports field widths and precisions, and the
modifiers `+', `-', ` ', `0', `#', `h' and `l'.  For more details on
the functioning of `printf', see the C Library Manual.