HPUX - Shell Programming - Loops

Arithmetic Evaluation Using let 

$ x=10

$ x=x+1

$ echo $x

x+1

$ x=10

$ let x=x+1  //let command enables shell scripts to use arithmetic expressions

$ echo $x

11

$ (( x=x+1 ))

$ echo $x

12

$ x=12

$ (( x>10 ))

$ echo $?

0

$ (( x<10 ))

$ echo $?

1

test - arithmetic evaluation, string, file 

let - arithmetic evaluation, arithmetic operator

while

ans=yes

while [ "$ans" = yes ]

do

    echo Enter a name

    read name

    echo $name >> file.names

    echo "Continue?"

    echo enter yes or no

    read ans

done

$ vi sum_them

"sum_them" 10 lines, 139 characters

x=1

sum=0

while (( x <= $1 ))

do echo enter $x th num

    read num

    (( sum = sum + num))

    let x=x+1

    echo sum is $sum

done

echo total $sum

until

ans=yes

until [ "$ans" = no ]

do

    echo Enter a name

    read name

    echo $name >> file.names

    echo "Continue?"

    echo enter yes or no

    read ans

done

for