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Shell Programming and Scripting

check if a string is numeric

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# 8  
Old 11-10-2011
awesome !!!! That worked.

But when I know that every time the user will input only positive numbers should i still include + or - in code ?
# 9  
Old 11-10-2011
Quote:
Originally Posted by megha2525
awesome !!!! That worked.

But when I know that every time the user will input only positive numbers should i still include + or - in code ?
Depends if you can guarantee that 100% of the time...otherwise *(+-) will take care of the absence or presence of a plus/minus sign so ultimately its your choice.
# 10  
Old 11-11-2011
try this out
name=+1234
Code:
echo $name | awk '/[+|-][[:digit:]]|[[:digit:]]/  {print -1}'

# 11  
Old 11-11-2011
Hi shamrock

Code:
var="12345"

if  [[ "$var" = *([+-])*([0-9])*(.)*([0-9]) ]]; then
    echo "it is numeric"
else
    echo "not numeric" 
fi

At the same time I also want to check if var is null. as in the user did not enter any value .The issue is the shell script must continue executing if the parameter is numeric ( integer or decimal ) or null .
How can i check for null value at the same time while i check for numeric values?
# 12  
Old 11-11-2011
I am fairly new to this forum so apologies if this has been posted before. Fairly close to Shamrock's, but I like this numeric check from Bolsky's "The New Kornshell":

Code:
#!/bin/ksh
isnum()
{
case $1 in
( ?([-+])+([0-9])?(.)*([0-9])?([Ee]?([-+])+([0-9])) )
return 0;;
( ?([-+])*([0-9])?(.)+([0-9])?([Ee]?([-+])+([0-9])) )
return 0;;
*) return 1;;
esac
}
myvar="-23.45"
isnum $myvar && echo "numeric" || echo "NOT numeric"

# 13  
Old 11-12-2011
Quote:
Originally Posted by megha2525
Hi shamrock

Code:
var="12345"

if  [[ "$var" = *([+-])*([0-9])*(.)*([0-9]) ]]; then
    echo "it is numeric"
else
    echo "not numeric" 
fi

At the same time I also want to check if var is null. as in the user did not enter any value .The issue is the shell script must continue executing if the parameter is numeric ( integer or decimal ) or null .
How can i check for null value at the same time while i check for numeric values?
Then all you have to do is separate the numeric regular expression from the one that is null by a vertical bar...
Code:
if  [[ "$var" = ?(""|*([+-])*([0-9])*(.)*([0-9])) ]]; then

This User Gave Thanks to shamrock For This Post:
megha2525
# 14  
Old 11-12-2011
Here is a simpler alternative if you are using ksh93:

Code:
declare -F foo
if (foo=$var) 2>/dev/null; then
    echo "it is numeric"
else
    echo "it is not numeric"
fi
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