Re: Capturing user input. ;P

..to get the newline out of the input
here's a trick I brewed using regexp and translit:

3a. Say the user enters their input, and you capture/store input
using the said method (so a macro `userParam' gets defined with
the input -- but, as of yet, it contains the newline):
define(askUser,enter pattern: [pushdef(userParam,esyscmd({ read a;echo
$a;}))dnl
askUser()

3b. So, use the following code to strip the newline, and store
the value without the newline in a macro `userParam_':
define(userParam_,[translit(userParam,userParam,regexp(userParam,[[^]\(\w\)\n[$]],[\0
]))])


This method also allows you to get around the single-line nature of
regexp().
Daniel.

On Thu, Jul 21, 2011 at 3:54 AM, daniel daniel <[email protected]>wrote:

> 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.
>