Shell scripting -Casting a string into a number

veryangryman

Short Question but i cant figure out...


I have a string , $RNC with a value of "RNC01"

I want to make it into just the number 1.

Tried doing this...

y= 'expr 0 + $RNC'


This doesnt work. Is there a way of doing this (other than using nawk)?

Webmonkey

What about $RNC = $RNC * 1 ?

Actually I don't know what your trying to do? - Can you explain bit more.

$RNC = 1

veryangryman

Ok.

I have a string that contains letters and a number (e.g. RNC01)

I want it to just contain the numbers so that i can do mathematical operations on it.

So i can do an if statement later on to check if its value is greater than 6.

Hope this helps

Webmonkey

I don't know what shell you are working with but could you not use regular expression substitution to replace all none numbers to nothing so you end up with the a number and then it might be possible to do math operations on it though it still a string - I amn't sure - I don't know if there is any such thing as casting in shelling scripting either.

Worth a try I guess -

daymobrew

Use sed.

# Displays RCN01
echo "RCN = $RCN"

# Extract numbers into a new variable.
numonly=`echo $var1 | sed 's/[^0-9]//g'`

# Add to the variable and display result (13)
y=`expr 12 + $numonly`
echo $y

carveone

veryangryman wrote: »

I have a string , $RNC with a value of "RNC01"

I want to make it into just the number 1.

As has been pointed out, there's sed which is the general tool to do this. Are you stuck with expr? expr can use regexps too, albeit in an odd way..

y=`expr $RNC : '\([0-9]+$\) + 0`

might work (can't try it myself at the moment)