You can print error messages using
Prints message and the rest of the arguments to standard error, separated by spaces. Standard error is used, regardless of the --debugfile option (see Invoking m4).
The expansion of
errprint is void.
errprint is recognized only with parameters.
errprint(`Invalid arguments to forloop ') error→Invalid arguments to forloop ⇒ errprint(`1')errprint(`2',`3 ') error→12 3 ⇒
A trailing newline is not printed automatically, so it should be
supplied as part of the argument, as in the example. Unfortunately, the
exact output of
errprint is not very portable to other
implementations: POSIX requires that all arguments be printed,
but some implementations of
m4 only print the first.
Furthermore, some BSD implementations always append a newline
errprint call, regardless of whether the last argument
already had one, and POSIX is silent on whether this is