Im trying to write a simple webpage on a raspberry pi with Ubuntu Mate 16.04.
There is something wrong with these comparisons, for where ctemp is 31, or any other temperature, I get the message, "I have no idea what the temperature is."
I think my comparisons are off, but I cannot seem to figure out how to get a proper comparison.
#!/bin/bash
echo "<html><body>"
#get temp too and show in images
sensor=`/opt/vc/bin/vcgencmd measure_temp | sed "s/[^0-9]//g"`
#sensor is 10 times higher than actual Core temp.
ctemp=$((sensor/10))
echo "Core Temp: " $ctemp
if [ "$ctemp" >= "20" ] && [ "$ctemp" < "38" ];then echo "<img src=\"cool.png\" alt=\"cool\">"
elif [ "$ctemp" >= "38" ] && [ "$ctemp" < "50" ];then echo "<img src=\"mid.png\" alt=\"Normal Operational Temprature\"><br>"
elif [ "$ctemp" >= "50" ];then echo "<img src=\"hot.png\" alt=\"Hot\">"
else echo "<br>I have no clue what temprature it is<br>"
fi1 Answer
From man bash:
string1 == string2 string1 = string2 True if the strings are equal. = should be used with the test command for POSIX conformance. When used with the [[ command, this performs pattern matching as described above (Compound Commands). string1 != string2 True if the strings are not equal. string1 < string2 True if string1 sorts before string2 lexicographically. string1 > string2 True if string1 sorts after string2 lexicographically. arg1 OP arg2 OP is one of -eq, -ne, -lt, -le, -gt, or -ge. These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively. Arg1 and arg2 may be positive or negative integers.So, rather than comparing with >= and < (string comparison), use -ge and -lt (numeric comparison).
