non biased randon number

README.md

@@ -3,8 +3,8 @@
 My collection of useful shell scripts.
 
 ### randint.sh 
-usage: randint <positive integer>   
-print in the terminal a random integer x with $` 0 \leq x \lt \$1`$
+usage: randint \<positive integer\> \[fast\]   
+print in the terminal a random integer x with $` 0 \leq x \leq \$1`$
 
 ### killwine.sh 
 kill every wine process including processes hanging

randint.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 if ! [[ "$1" =~ ^[0-9]+$ ]]; then
-    echo "Usage: randint <positive integer>"
+    echo "Usage: randint <positive integer> [fast]"
     exit 1
 fi
 number=$1
@@ -8,5 +8,13 @@ ceiling=$(echo "l($number +1)/l(2)" | bc -l | awk '{
     bits = ($1 == int($1)) ? $1 : int($1) + 1;
     print int( (bits + 7) / 8 )
 }')
-random_num=$(xxd -p -l $ceiling /dev/urandom | tr -d '\n' | awk -v num="$number" '{print strtonum("0x" $0) % num}')
+
+if [[ "$2" == "fast" ]]; then
+    random_num=$(xxd -p -l $ceiling /dev/urandom | tr -d '\n' | awk -v num="$number+1" '{print strtonum("0x" $0) % num}')
+else
+    while :; do
+        random_num=$(xxd -p -l $ceiling /dev/urandom | tr -d '\n' | awk '{print strtonum("0x" $0)}')
+        (( random_num < number )) && break
+    done
+fi
 echo $random_num