CODEWITHSUNDEEP
bashshell
jagatjyoti
jagatjyoti

Reputation: 717

Compare two alphanumeric variables mixed with special expression in shell script

I want to compare two alphanumeric strings and below is the bash expression I think should do the job. But I'm getting blank result. Please advise. 

:~$ echo $tempnow $threshold
+60.0°C +80.0°C

:~$ res=`echo "$tempnow $threshold" | awk '{ if($1 > $2) print "Exceeds"; else echo "Normal" }'`
:~$ echo $res

:~$

Upvotes: 0

Views: 937

Answers (3)

Lalit Somnathe
Lalit Somnathe

Reputation: 111

try below :-

res=`echo "$tempnow $threshold" | awk '{ if($1 > $2) print "Exceeds"; else print "Normal" }'`

Upvotes: 0

anubhava
anubhava

Reputation: 785721

There is no echo in awk.

You can use:

echo '+90.0°C +80.0°C' | awk '{ print ($1+0 > $2+0 ? "Exceeds" : "Normal") }'
Exceeds

echo '+60.0°C +80.0°C' | awk '{ print ($1+0 > $2+0 ? "Exceeds" : "Normal") }'
Normal

Also note use of +0 to convert fields into numeric values.

Upvotes: 3

Tom Fenech
Tom Fenech

Reputation: 74685

You have written echo instead of print in your awk script.

This will be interpreted as the name of a function or variable, which doesn't exist, then it will be coerced to an empty string and concatenated with the string "Normal". The result will be discarded.

I would recommend writing your script as follows:

res=$(awk '{ print ($1 > $2 ? "Exceeds" : "Normal") }' <<<"$tempnow $threshold")

This uses <<< to pass the string over standard input to awk. The result of the ternary operator is printed and stored in the variable $res.

Bear in mind that you are currently comparing strings, so you will run into problems in situations such as this:

$ tempnow=+9.0°C
$ threshold=+80.0°C
$ awk '{ print ($1 > $2 ? "Exceeds" : "Normal") }' <<<"$tempnow $threshold"
Exceeds

Upvotes: 1

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