Bash : how do i check the user input and make sure is only chracter or only number ?

CheeSen · 09-07-2008, 02:29 AM

thedonkdonk · 09-07-2008, 02:53 AM

Use a regex.

CheeSen · 09-07-2008, 03:05 AM

if i only want to check the first digit wheter is a number "0" or not .
how to do it

thedonkdonk · 09-07-2008, 03:19 AM

That is a lot easier. Do something like this.

Code:

#!/bin/bash
echo "Enter 0, then press <ENTER>."
read INPUT # or what ever you want to call the variable.
if [[ "$INPUT" != 0 ]]
then
echo "You pressed $INPUT, which is not the same as 0. Goodbye."
exit
else
echo "Congratulations! You can read and type. You win!"
exit
fi

CheeSen · 09-07-2008, 03:28 AM

sorry, i mean the first character .
example user enter 0asdg

then system detected that user input no avalaible because start at 0

colucix · 09-07-2008, 03:54 AM

First you can try parameter substitution to extract the first character from the input string. Second, if using BASH version 3, which supports the comparison operator to match against a regular expression =~, you can do something like this:

Code:

#!/bin/bash
read -p "Enter a string: " string
if [[ ${string:0:1} =~ [[:digit:]] ]]
then
   echo digit
elif [[ ${string:0:1} =~ [[:alpha:]] ]]
then
   echo character
else
   echo other
fi

If backward compatibility is an issue, or if you don't have BASH version 3, use grep -q instead of the double brackets expressions.

lipun4u · 09-07-2008, 07:02 AM

is the following code does your work ???

Code:

echo -n "Enter user i/p : "
read ip
first_char=`expr substr $ip 1 1`
if [ $first_char = "0" ]
then
	echo user i/p not available
else
	echo user i/p available
fi

ghostdog74 · 09-07-2008, 09:26 AM

@OP, check out the learning bash link in my sig.

pixellany · 09-07-2008, 09:43 AM

OP appears to be posting a series of homework questions. In another thread, I have asked him/her to describe his/her objectives. We should also be looking for any evidence of what solutions OP has already attempted.

colucix · 09-07-2008, 11:14 AM

Quote:

Originally Posted by pixellany

OP appears to be posting a series of homework questions. In another thread, I have asked him/her to describe his/her objectives. We should also be looking for any evidence of what solutions OP has already attempted.

I did not think about homework, until I saw the other posts... sorry.

pixellany · 09-07-2008, 03:15 PM

Quote:

Originally Posted by colucix

I did not think about homework, until I saw the other posts... sorry.

Eeeek!! Please don't apologize. I respond to these things all the time.

I just seem to have an ultra-sensitive homework detector.....