GPIO Bash Scripts

[emcsquirreled]

I was working with the wiringPi library, and wrote the following scripts for debugging purpose. I thought somebody might like to use them (bash is hard with no experience or reference books ), so here goes!

poll-gpio.sh

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#!/bin/bash

clear

while test 1 -eq 1
do
    ./read-gpio-all.sh
    for i in {1..5000}
    do
        echo -n
    done
    clear
done

read-gpio-all.sh

Code: Select all

#!/bin/bash

for counter in {0..7}
do
    echo -n "pin "
    echo -n $((counter))
    echo -n " is "
    gpio read $((counter))
done

[jojopi]

Code: Select all

    for i in {1..5000}
    do
        echo -n
    done

I assume this is to introduce a delay. It would be better to use "sleep 1" instead, because it does not waste cpu time, and will not vary with overclocking. On some systems sleep can only wait for an integer number of seconds, but on Linux you can use fractions like "sleep 0.2" as well.

[emcsquirreled]

Code: Select all

    for i in {1..5000}
    do
        echo -n
    done

I assume this is to introduce a delay. It would be better to use "sleep 1" instead, because it does not waste cpu time, and will not vary with overclocking. On some systems sleep can only wait for an integer number of seconds, but on Linux you can use fractions like "sleep 0.2" as well.

That was designed to delay the code, and prevented all the reads and clears from creating a rapidly flashing screen, which was very hard to read. I am fairly new to shell scripting, so sorry for the dumb mistake.

I cannot find a way to edit my original post, but the script should read like so:

poll-gpio.sh

Code: Select all

#!/bin/bash

clear

while test 1 -eq 1
do
    ./read-gpio-all.sh
    sleep 1
    clear
done

[BlackJack]

@emcsquirreled: Both scripts could be expressed more concise:

Code: Select all

#!/bin/bash

while true
do
    clear
    ./read-gpio-all.sh
    sleep 1
done

Code: Select all

#!/bin/bash

for counter in {0..7}
do
    echo "pin $counter is $(gpio read $counter)"
done

Edit: And instead of the first script you could use ``watch``:

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$ watch --help
Usage: watch [-bcdhnptvx] [--beep] [--color] [--differences[=cumulative]] [--exec] [--help] [--interval=<n>] [--no-title] [--version] <command>
  -b, --beep                            beep if the command has a non-zero exit
  -d, --differences[=cumulative]        highlight changes between updates
                (cumulative means highlighting is cumulative)
  -e, --errexit                         exit watch if the command has a non-zero exit
  -h, --help                            print a summary of the options
  -n, --interval=<seconds>              seconds to wait between updates
  -p, --precise                         precise timing, ignore command run time
  -v, --version                         print the version number
  -t, --no-title                        turns off showing the header
  -x, --exec                            pass command to exec instead of sh

[emcsquirreled]

@emcsquirreled: Both scripts could be expressed more concise.
Edit: And instead of the first script you could use ``watch``:

Thank you! As I said in the first post, I have self-taught myself bash from a single reference book and trial-and-error. This is my first published script, so all the input and corrections are greatly appreciated. Apparently I had some bad habits forming, so it is good they got killed before they grew too far.

The new script should read like so (poll-gpio.sh is no longer necessary):

read-gpio-all.sh

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#!/bin/bash
for $counter in {0..7}
do
    echo "pin $counter is $(gpio read $counter)"
done

And then you run it like so:

Command Line

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watch -n 1 ./read-gpio-all.sh

[gordon@drogon.net]

There are also some examples online which I put together for the various projects - e.g. the Tuxx Traffic light crossing thing is:

https://git.drogon.net/?p=gpioExamples; ... xx/tuxx.sh

-Gordon