Capturing user input. ;P

Here is a neat m4 hack I've come up with to capture user input from within
m4.

There are two variations I propose to capture user input:

1. The first method captures user input from the shell, exploiting pipelines
from the shell and how this relates to /dev/fd/0:
Code:
dnl call this file m4stdin.m4
pushdef(userParam,`include(/dev/fd/0)')
eval(userParam+1)

Discussion:
Given the shell command: { echo 1|m4 m4stdin.m4;}
the output will be: 2

2. The second method exploits the `read' shell builtin command:
Code:
changequote([,])
define(askUser,enter A or B: [pushdef(userParam,esyscmd({ read a;echo
$a;}))dnl
ifelse(userParam,[A
],[include(110721m4a.m4)],dnl
ifelse(userParam,[B
],[include(110721m4b.m4)]))][popdef([userParam])])dnl
askUser()

Discussion:
on running this code, the user will be prompted with the text: "enter A or
B: "
the user will then type either an A or a B; then, in this example, i've
implemented
conditional file inclusion (i.e., if the user inputs A, then 110721m4a.m4
will be
evaluated; if the user inputs B, then 110721m4b.m4 will be included and
evaluated.)



;P
Daniel.