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04-27-2009
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try this:
Code:
function validatenumber
{
number="$1"
if [ -z $number ];then
echo "not something" > &2;return 1
fi
if [ "${number%${number#?}} = "-" ]; then
testvalue="${number#?}"
fi
if [ "${number%${number#?}} = "+" ]; then
testvalue="${number#?}"
fi
nodigits="$(echo $testvalue | sed 's/[[:digit:]]]//g')"
if [ ! -z $nodigits ]; then
echo "Invalid Number" > &2
return 1
fi
return 0
}
if validatenumber "$1"; then
echo "No is a valid integer"
fi
cheers, Devaraj Takhellambam |
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09-21-2005
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The problem can easily be solved by considering what a "number" is actually and since this is a good opportunity to show how to develop regular expressions I will explain that in greater detail:
1st Try The only characters allowed should be 0-9. This covers for "123", but not for "123.0". Hence 2nd Try Only 0-9 are allowed, save for exactly 1 character, which may be a fullstop. This definition covers "123" and "456.78", leaves out (quite correctly) "123.456.789", but doesn't cover "-123.0" or "+123.0". Hence 3rd Try In addition to 2nd Try the first character may be "+" or "-" optionally. This covers every number and leaves out any non-number, so this solution is perfect. We develop a simple sed-statement from there, by consecutively throwing out all "allowed" chars and look, if something remains. If something remains it is non-numeric, if not, then it is numeric: Code:
if [ -n "$( print - "$VarInQuestion" |\
sed 's/^[+-]//;s/[0-9]//g;s/\.//' \
)" ] ; then
print - "$VarInQuestion is non-numeric"
else
print - "$VarInQuestion is numeric"
fi
s/^[+-]// - see 3rd try, we chop off leading +/- signs s/[0-9]//g - see 1st try, we throw out all numerical digits s/\.// - see 2nd try, we throw out one possible decimal point bakunin |
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09-21-2005
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number or not
if u r using tcl or perl there is finction calles isnumber
if [ isnumber $a ] { }  |
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04-10-2009
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Code:
$ $ x=1; if [ "`expr $x - $x 2>/dev/null`" == "0" ]; then echo is number; else echo not number; fi is number $ x=-1; if [ "`expr $x - $x 2>/dev/null`" == "0" ]; then echo is number; else echo not number; fi is number $ x=a; if [ "`expr $x - $x 2>/dev/null`" == "0" ]; then echo is number; else echo not number; fi not number $ x=1a; if [ "`expr $x - $x 2>/dev/null`" == "0" ]; then echo is number; else echo not number; fi not number $ |
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04-27-2009
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This solution is better as it works for decimals as well:
Code:
$ x=a; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi not number $ x=9a; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi not number $ x=9; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi is number $ x=9.1; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi is number $ x=-9.1; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi is number $ x=-9; printf "%g" $x >/dev/null 2>&1; if [ $? -eq 0 ]; then echo is number; else echo not number; fi is number |
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