is there a val() or int() kind of functions for shell

Jykke · 04-08-2008, 09:39 AM

I am looking for a val() function. I am reading in an input via sed and depending it might have string as content and this results in an error later on the program. I would like to have a check if there is some string to convert it in a number like in basic val("blabla") output is 0

Is there a way to accomplish this in shell?

Max Rebo · 04-08-2008, 09:47 AM

Quote:

Originally Posted by Jykke

I am looking for a val() function. I am reading in an input via sed and depending it might have string as content and this results in an error later on the program. I would like to have a check if there is some string to convert it in a number like in basic val("blabla") output is 0

Is there a way to accomplish this in shell?

Look at the follwing page:

http://steve-parker.org/sh/test.shtml

Two-thirds down the page they show an example of a number-guessing game where they validate the input to be numbers only. It may be what you need. Search for "guess the magic number" when you have the page open.

HTH

prad77 · 04-08-2008, 10:05 AM

try doing a printf with the interger format %d...

like for example ,
awk '{printf "%d", $1}' filename >newfilename.

Gentoo

Max Rebo · 04-09-2008, 09:10 AM

Quote:

Originally Posted by prad77

try doing a printf with the interger format %d...

like for example ,
awk '{printf "%d", $1}' filename >newfilename.

I don't think he wants to format/print the number, he wants a function that will "fail" the convert so that he can know the value tested is -not- a valid number. The link I provided uses grep to test the value.

So I guess he can create a function (not tested at all):

Code:

function isNumber()
{
   echo $1 | grep "[^0-9]" > /dev/null 2>&1
   if [ "$?" -eq "0" ]; then
      return false
   else
      return true
   fi
}

Go to my suggested link above and play with this if you are interested.

sundialsvcs · 04-09-2008, 10:43 PM

Bear in mind, though, that a typical Unix/Linux environment will provide you with several good, free, already-installed high level programming languages. "Shell scripting" is really not designed to be a general-purpose programming language, and so I think it is generally quite un-productive to waste your time trying to press it into such service. If you (probably) have Perl, Python, PHP, and Ruby at your beck-and-call ... pick one of those.

A program written in any of those tools is absolutely indistinguishable ... when it runs ... from a mind-mess that was cobbled together using bash. You're not here to waste your own time: use the best tool for the job.

Jykke · 04-20-2008, 06:43 AM

Quote:

Originally Posted by prad77

try doing a printf with the interger format %d...

like for example ,
awk '{printf "%d", $1}' filename >newfilename.

Gentoo

No, thanks, this was already quite what I was looking for - I just needed to direct stdout via awk, but the formulation was to the point.

shell is quite the correct choice if I already execute other commands from shell script and just want to process their outputs...

PTrenholme · 04-21-2008, 03:15 PM

From man bash

Code:

       ((expression))
              The expression is  evaluated  according  to  the  rules
              described  below  under  ARITHMETIC EVALUATION.  If the
              value of the expression is non-zero, the return  status
              is  0;  otherwise  the  return  status  is  1.  This is
              exactly equivalent to let "expression".