Use AWK and SED to read a sensor, and output value to html file

Question

I have a TP-Link WR703N flashed with openWRT, connected to a one wire DS18B20 temperature sensor. My goal is to get the router to show the current temp. on a web page. I am using digitemp to read the sensor

When i issue the following command:

root@OpenWrt:~# digitemp_DS9097 -a

The reply from digitemp is:

DigiTemp v3.5.0 Copyright 1996-2007 by Brian C. Lane
GNU Public License v2.0 - http://www.digitemp.com
Feb 23 02:46:31 Sensor 0 C: 25.44 F: 77.79

I found this example, where a CRON-script with AWK and SED is used to read the c value, and update a HTML-file.

When i try to paste the script to /etc/crontabs/root, some of the qoutation marks are replaced with ... in the VI editor. I tried to use the Nano editor instead, but it just replaces the qoutation marks with ^?^?^. I do not understand AWK as well as I wish, so i have trouble figuring outh wether the author of the script has used wrong qoutation-marks, or if there is another reason me not being able to input the right characters.

Any input would be greatly appreciated.

Answer 1

It's the formatting of that blog post, it's got non-ASCII quotes. Just edit them to fix.

*/1 * * * * TEMP=$(digitemp_DS9097 -a | grep -i sensor | awk '{print $7}'); sed -i -r "14s,>[^<]*</,>${TEMP}</," /www/index.html

I'm not sure if the rest of the line is right though, my sed doesn't have that -r flag, and the script tries to change line 14 (hence 14s...) which is very picky on whether you copied the html from the blog exactly. I used this instead:

*/1 * * * * TEMP=$(digitemp_DS9097 -a |grep -i sensor | awk '{print $7}');sed -i.bak "s,\\(66cc00.*\">\\)[^<]*</,\\1$TEMP</,"  /www/index.html

which matches on the colour number on the line instead. The extra \\(...\\) are capturing that so that I can use it again in the replacement as \\1.

I've just read the manual for digitemp_DS9097 (http://www.linuxcertif.com/man/1/digitemp_DS9097/) - you'd be better running it as digitemp_DS9097 -q -t 0 -O"%.2C", which gives you the output directly as a single Centigrade number with no need for grep/awk. eg:

*/1 * * * * TEMP=$(digitemp_DS9097 -q -t 0 -O"%.2C");sed -i.bak "s,\\(66cc00.*\">\\)[^<]*</,\\1$TEMP</,"  /www/index.html