BASH: testing that arguments are a list of numbers - regex

Question

I am trying to test that an infinite number of arguments ( "$#" ) to a bash script are numbers ( "#", "#.#", ".#", "#.") delimited by spaces (i.e. # # # # ...). I have tried:
[ "$#" -eq "$#" ]
similar to what I found in this answer but I get:
"[: too many arguments"
and I have also tried regular expressions but it seems once the regular expression is satisfied anything can come afterwards. here is my code:
if (($# >=1)) && [[ "$#" =~ ^-?[[:digit:]]*\.?[[:digit:]]+ ]]; then
it also needs to not allow "#.." or "..#"

Answer 1

I don't think that [ "$#" -eq "$#"] is going to work somehow.
A loop like this could help to read each argument and detect if it is an integer number (bash does not handle decimals):
for i in $#;do
if [ "$i" -eq "$i" ] 2>/dev/null
then
echo "$i is an integer !!"
else
echo "ERROR: not an integer."
fi
done
In your case , to determine if argument is a valid integer/decimal number instead of all those regex ifs, we can simply divide the number with it's self using bc program of bash.
If it is a valid number will return 1.00
So in your case this should work:
for i in $#;do
if [[ "$(bc <<< "scale=2; $i/$i")" == "1.00" ]] 2>/dev/null;then
echo "$i is a number and thus is accepted"
else
echo "Argument $i not accepted"
fi
done
Output:
root#debian:# ./bashtest.sh 1 3 5.3 0.31 23. .3 ..2 8..
1 is a number and thus is accepted
3 is a number and thus is accepted
5.3 is a number and thus is accepted
0.31 is a number and thus is accepted
23. is a number and thus is accepted
.3 is a number and thus is accepted
Argument ..2 not accepted
Argument 8.. not accepted

Answer 2

$# is an array of strings. You probably want to process the strings one at a time, not all together.
for i; do
if [[ $i =~ ^-?[[:digit:]]+\.?[[:digit:]]*$ ]] || [[ $i =~ ^-?\.?[[:digit:]]+$ ]]; then
echo yes - $i
else
echo no - $i
fi
done

Answer 3

In bash there is pattern matching with multiplier syntax that can help your problem. Here is a script to validate all arguments:
for ARG ; do
[[ "$ARG" = +([0-9]) ]] && echo "$ARG is integer number" && continue
[[ "$ARG" = +([0-9]).*([0-9]) ]] && echo "$ARG is float number" && continue
[[ "$ARG" = *([0-9]).+([0-9]) ]] && echo "$ARG is float number" && continue
[[ "$ARG" = -+([0-9]) ]] && echo "$ARG is negative integer number" && continue
[[ "$ARG" = -+([0-9]).*([0-9]) ]] && echo "$ARG is negative float number" && continue
[[ "$ARG" = -*([0-9]).+([0-9]) ]] && echo "$ARG is negative float number" && continue
echo "$ARG is not a number."
done
The for loop automatically uses the arguments received by the script to load the variable ARG.
Each test from the loop compares the value of the variable with a pattern [0-9] multiplied with + or * (+ is 1 or more , * is zero or more), sometimes there are multiple pattern next to each other.
Here is an example usage with output:
$ ./script.sh 123 -123 1.23 -12.3 1. -12. .12 -.12 . -. 1a a1 a 12345.6789 11..11 11.11.11
123 is integer number
-123 is negative integer number
1.23 is float number
-12.3 is negative float number
1. is float number
-12. is negative float number
.12 is float number
-.12 is negative float number
. is not a number.
-. is not a number.
1a is not a number.
a1 is not a number.
a is not a number.
12345.6789 is float number
11..11 is not a number.
11.11.11 is not a number.

Answer 4

I shall assume that you meant a decimal number, limited to either integers or floating numbers from countries that use a dot to mean decimal point. And such country does not use a grouping character (1,123,456.00125).
Not including: scientific (3e+4), hex (0x22), octal (\033 or 033), other bases (32#wer) nor arithmetic expressions (2+2, 9/7, 9**3, etc).
In that case, the number should use only digits, one (optional) sign and one (optional) dot.
This regex checks most of the above:
regex='^([+-]?)([0]*)(([1-9][0-9]*([.][0-9]+)?)|([.][0-9]+))$'
In words:
An optional sign (+ or -)
Followed by any amount of optional zeros.
Followed by either (…|…|…)
A digit [1-9] followed by zero or more digits [0-9] (optionally) followed by a dot and digits.
No digits followed by a dot followed by one or more digits.
Like this (since you tagged the question as bash):
regex='^([+-]?)([0]*)(([1-9][0-9]*([.][0-9]+)?)|([.][0-9]+))$'
[[ $n =~ $regex ]] || { echo "A $n is invalid" >&2; }
This will accept 0.0, and .0 as valid but not 0. nor 0.
Of course, that should be done in a loop, like this:
regex='^([+-]?)([0]*)(([1-9][0-9]*([.][0-9]+)?)|([.][0-9]+))$'
for n
do m=${n//[^0-9.+-]} # Only keep digits, dots and sign.
[[ $n != "$m" ]] &&
{ echo "Incorrect characters in $n." >&2; continue; }
[[ $m =~ $regex ]] ||
{ echo "A $n is invalid" >&2; continue; }
printf '%s\n' "${BASH_REMATCH[1]}${BASH_REMATCH[3]}"
done