Nested loop in shell

I am a beginner at shell programming. I have a problem related to nested loops in shell scripts. I want to get output like this:

Input: 4

Output:

*
**
***
****

This is the script I am using so far:

echo "input : "
read a
for开发者_开发知识库 ((i=0; i<a; i++))
do
   for ((j=0; j<i; j++))
   do
       echo "*"
   done
   echo "\n"
done

When trying to execute my program I get an error: Bad for looping.

Thanks in advance.

try this

echo "input : "
read a
for ((i=0; i<a; i++))
do
   for ((j=0; j<=i; j++))
   do
       printf "*"
   done
   echo
done

To not print newlines, you can use printf (or the echo -n but is not as portable as printf)

I don't get any error with the script! Though the echo needs to be different like below:

echo "input : "
read a
for ((i=0; i<a; i++))
do
   for ((j=0; j<i; j++))
   do
       echo -ne "*"
   done
   echo -ne "\n"
done

You might try adding $ in front of the variables while accessing them though. It is not giving any errors for me.

#!/bin/bash

print_starry_row()
{
    n="$1"
    for ((i=0;i<n;i++))
    {
        echo -n "*"
    }
    echo
}

read -p "Enter number of stars? " num

if [[ "$num" -eq $num ]]
then
    for ((i=1;i<=num;i++))
    {
        print_starry_row $i
    }
else
    echo "You must enter a valid integrer"
fi