Remove char if not a number


 
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# 1  
Remove char if not a number

I need to write a BASH script that takes a 2 character string and removes the second character if it is not a digit e.g.

If the string is numberical value >9 e.g. string1 = '34' then leave string1 = '34'.

However if the string is <10 e.g. string1 = '3X' then remove the second char (which can be any character, it's whatever was in memory) so that '3X' will now be '3'.

I was thinking about using ASCII values to determine whether the second character is a number.

Here's my attempt (I'm a newbie):

Code:
#!/bin/bash
 
if [ [string1[1]<'48'] || [string1[1]>'57'] ] # if 2nd char <0 or >9
then
        string1[1]="NOT SURE WHAT TO PUT HERE!!"
fi

# 2  
Try something like...
Code:
$ string1='3X'

$ case $string1 in [0-9][0-9]) : ;; [0-9]?) string1=${string1:0:1} ;; esac

$ echo $string1
3

$

This User Gave Thanks to Ygor For This Post:
# 3  
Would :-
Code:
echo "$string" | tr -d "[a-z][A-Z]"

... do the trick or does this not handle enough possible characters?

Perhaps:-
Code:
#!/bin/ksh
c1="${string%?}"                 # Get 1st character
c2="${string#?}"                 # Get 2nd character

c2=`echo ${c2}|egrep "[0-9]"`    # Get only numeric value or null for 2nd

string="${c1}${c2}"              # Stick string back together




I hope that this helps,
Robin
Liverpool/Blackburn
UK
This User Gave Thanks to rbatte1 For This Post:
# 4  
Quote:
Originally Posted by Ygor
Try something like...
Code:
$ string1='3X'
 
$ case $string1 in [0-9][0-9]) : ;; [0-9]?) string1=${string1:0:1} ;; esac
 
$ echo $string1
3
 
$

Thanks for the reply it worked perfectly.

However I don't fully understand it.
If the string is any 2 digits do nothing. That part is ok.
The next part, if the string is a number and any other char, then replace the string with ${string1:0:1}. Can you explain the string1:0:1 part please? Thanks
# 5  
read man bash on Parameter Expansion / Substring Expansion.
This User Gave Thanks to RudiC For This Post:
# 6  
Code:
$ string=3X; echo "${string//[!0-9]/}"
3

# 7  
Quote:
Originally Posted by RudiC
read man bash on Parameter Expansion / Substring Expansion.
Code:
${parameter:offset:length}

That's exactly what I wanted but had no idea where to look.

Last edited by Franklin52; 08-23-2013 at 12:01 PM.. Reason: Please use code tags
 

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