NumberSting bash program

[Garrett85]

I'M trying to write a small program that will take a number as input, anything from 1 to 999,999,999,999 and return it as a string. I've already created a flowchart in dia and now I'M trying to write on top of that chart in bash. I'M very new to bash by the way.

The first thing I need to do is recieve the number a figure out how many groups of three are in the number. Based on counting by threes, if there's an odd number like 4 or 5 that still need t ocount as a groupd. Examples: ### = 1 groups, #,### = 2 gropus, ##,### = 2 groups.

I think I need to dived by 3 what the answer will be my number but I need to account for the remainders as well. Any advice? Thanks.

[atreyu]

Hi,

To get the number in bash, you can either provide the number as a command line argument to the script (i.e., you provide it when you call the script), or you can pass it via STDIN (using the bash built-in read).

example of the former:

#!/bin/bash
foo=$1
echo "You said '$foo'"

call it like this:

./script.sh 1,234

example of the latter:

#!/bin/bash
read -p "Enter a number: " foo
echo "You said '$foo'"

call it like this:

./script.sh

Note that you'll want to verify that $foo is a number, before going any further (i.e., use a grep regex).

To determine how many groups are in the number, you could either count the commas using grep and the "-c" option (assuming they are provided), or just use bash built-in arithmetic (e.g., if [ $foo -gt 999 ]; then) to see if the number is greater than 999 or 999,999, etc.

[watael]

how are given numbers? with or without coma?

with comas:

• put the number in a variable
• replace every coma by a space
• put the "new" variable into an array
• see how many items has got the array

var=10,000,000
array=( ${var//,/ } )
echo ${#array[@]}

without comas, you need to divide the number of digits in the number by three, and add one if the modulo is more than zero.

var=1,000,000
echo "$(( (${#var} % 3 ?1:0) + (${#var}/3) )) group(s)"

[Garrett85]

I was going to do this without commas and get the number through read. I know I needed to divid by 3 but just wasn't sure how to deal the the remainder.

how are given numbers? with or without coma?

with comas:

• put the number in a variable
• replace every coma by a space
• put the "new" variable into an array
• see how many items has got the array

var=10,000,000
array=( ${var//,/ } )
echo ${#array[@]}

without comas, you need to divide the number of digits in the number by three, and add one if the modulo is more than zero.

var=1,000,000
echo "$(( (${#var} % 3 ?1:0) + (${#var}/3) )) group(s)"

[Irithori]

You might want to have a look at printf and the radix character.

man 1 printf
man 3 printf

[Garrett85]

What is ?1:0 and what is group? Is group a bash keyword?

[watael]

see ternary operator
and
man bash arithmetic evaluation