Bash exec in infinite while loop doesn't work

Question

#!/bin/bash 
while :
do
    echo twerkin
    exec free -h > /ver/www/raspberry/load.txt
    exec /opt/vc/bin/vcgencmd measure_temp > /var/www/raspberry/heat.txt
done

This is what I made, I am going to read it on my website, but thats not the problem. The problem is that it gives me this error:

pi@raspberrypi ~ $ sh showinfo.sh
showinfo.sh: 7: showinfo.sh: Syntax error: "done" unexpected (expecting "do")

I'm running this on my raspberry pi with Raspbian (Debian Wheezy)

Running a Bash script with sh is always an error. But your script works fine here (apart from the obvious misunderstanding of what exec does) without errors. — tripleee
– tripleee, Commented Oct 22, 2014 at 10:32
Why is it not working over here than? Is it because of the stripped out version of Debian Wheezy??? (Raspbian) — Wouter Doeland
– Wouter Doeland, Commented Oct 22, 2014 at 10:34

tripleee · Accepted Answer · 2014-10-22 10:29:44Z

2

You don't seem to understand what the exec keyword does. It replaces your current script (basically, thewhile loop) with the free command.

To run a command, simply specify it.

#!/bin/bash

while : ; do
    free -h
    /opt/vc/bin/vcgencmd measure_temp 
done

(I omitted the redirections because you were overwriting the old results on each iteration. What do you actually want?)

answered Oct 22, 2014 at 10:29

tripleee

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3 Comments

Wouter Doeland Over a year ago

How can I let bash run another program than?

Wouter Doeland Over a year ago

I want output from every thing I run in 2 seperate files, so free- h in /var/www/raspberry/load.txt and the output from /opt/vc/bin/vcgencmd measure_temp in /var/www/raspberry/heat.txt, so that I can read them with HTML.

tripleee Over a year ago

They are not HTML. If you want to append to the file on each iteration, use >>.

user3694243 · Accepted Answer · 2014-10-22 11:33:41Z

0

try to change few things in your script

#!/bin/bash 

while : ;
do
    echo twerkin

    #### commands to execute are not need to be prefixed with exec
    #### + concatenate output with >>
    free -h >> /ver/www/raspberry/load.txt

    #### same here
    /opt/vc/bin/vcgencmd measure_temp >> /var/www/raspberry/heat.txt

    #### you probably would want to add a delay here, because in other way
    #### the script will be executed probably way too fast
    # sleep 0.01

done

answered Oct 22, 2014 at 11:33

user3694243

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2 Comments

Wouter Doeland Over a year ago

Thanks for you input! But it gives this error: pi@raspberry ~ $ ./showinfo.sh : no such file or directory

Wouter Doeland Over a year ago

I found another way to do it without the loop, I don't know why it doesn't work. Has it anything to do with SSH?

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