find string in file - test the value

zimbot · 09-10-2009, 06:13 PM

Friends,

i have a com port gizmo [ vk011 ]
This gizmo gives the temp of the room.

I can connect to it via mini com
and it spits out line after line of

Sensor 1 +70.13 DegF Hi +77.56 DegF Low +29.75 DegF
Sensor 1 +70.13 DegF Hi +77.56 DegF Low +29.75 DegF
Sensor 1 +70.13 DegF Hi +77.56 DegF Low +29.75 DegF

My Goal is to have an ALARM if the room gets above a num ( 80 )

There may be a better way but so far I have this
i can write 1 line to a text file

like this

head -1 /dev/ttyS0 > 01.txt
It runs and then stops - i get
Sensor 1 +70.13 DegF Hi +77.56 DegF Low +29.75 DegF

so now i wonder if I can
1-- read the line from the file 01.txt
2-- look at the characters 11 & 12 - basically see the 70.
3-- do an 'if that num (70) is greater than some value I declare
like say 80' do something

I already know ( i think ) how to send an email in a bash.
that would be the something I would like to do.

now it might be possible to do that without writting to a file-- but this is what i have so far.

MS3FGX · 09-10-2009, 06:34 PM

There would be many ways to do this, but the first script that came to mind was:

Code:

#!/bin/sh
# 
# Script to trigger an alarm past a certain temperature

# Alert temp
ALARM="80"

# Get just the temperature value
TEMP=`head -1 /dev/ttyS0 | awk '{print $3}' | cut -c2-3`

# Compare to trigger temperature
if [ "$TEMP" -ge "$ALARM" ]; then
     # Put command to run here
     echo "Temperature alarm!"
fi

That was off the top of my head, so there might be some syntax issues there. But I am pretty sure that will do what you want.

zimbot · 09-11-2009, 07:25 AM

Yes that works
putting the alarm val in a var - i knew before
but the means to get the string - to parse the output - OUTSTANDING!

TEMP=`head -1 /dev/ttyS0 | awk '{print $3}' | cut -c2-3`

awk - print $3 gets the 3rd colum and piped into cut getting #2 & #3 pos
so that TEMP is that num

then the if the -ge for greater ( i never knew ... )

# Compare to trigger temperature
if [ "$TEMP" -ge "$ALARM" ]; then

wow thnaks

also -- i caused me to read about awk.
amazing written ( in part ) by the fellow who wrote C [ mr K of awk ]

again , thanks!

I trullllly love this way of learning.

I will be able to USE this!