Bash script unexpected result for while loop

I have following bash script to stop Apache server. I am not getting error but an unexpected result.

#!/bin/bash

/etc/init.d/httpd stop
if [[ $? -ne 0 ]]
then
    exit 1
fi
RTN=10
while [[ $RTN -gt 0 ]]
echo "Before" $RTN
do
    sleep 5
    RTN=`ps -C httpd | wc -l`
    RTN=$(( RTN - 1 ))
echo "After" $RTN
done 

exit 0

I got the following answer which I do not expect to be, with an infinite printing:

Before 10
After 0

Before 0
After 0

Before 0
After 0

I expect to print:

Before 10
After -1 
#and exit here

Could anybody please tell me what is happening?

Answer

This doesn’t work the way you seem to think it does:

while [[ $RTN -gt 0 ]]
echo "Before" $RTN
do

You want the echo to come after the do. With it before the do, it’s part of the list-1 condition rather than the list-2 body. And, as per the bash docs (my bold):

The while command continuously executes the list list-2 as long as the last command in the list list-1 returns an exit status of zero.

You can see the difference between the following script, similar to yours:

#!/usr/bin/bash
RTN=2
while [[ $RTN -gt 0 ]]
echo "Before" $RTN
do
    sleep 1
    RTN=$(( RTN - 1 ))
echo "After" $RTN
done

which outputs (ad infinitum):

Before 2
After 1
Before 1
After 0
Before 0
After -1
Before -1
After -2
Before -2

When you move the echo to inside the body:

#!/usr/bin/bash
RTN=2
while [[ $RTN -gt 0 ]]
do
    echo "Before" $RTN
    sleep 1
    RTN=$(( RTN - 1 ))
    echo "After" $RTN
done

it then terminates properly:

Before 2
After 1
Before 1
After 0
<returns to prompt>

Once that change is made, the loop terminates correctly, given the values being generated by your ps command.

---

Additionally, if you want to find out what’s in the process list (and probably causing an result of zero rather than negative one), output the process list before checking the count:

:
ps -C httpd                 # Add this line temporarily.
RTN=`ps -C httpd | wc -l`
: