I'm having a heck of a time removing characters in Bash. I have a string that's formatted like temp=53.0'C. I want to remove everything thats not 53.0.
I'm normally a Python programmer, and the way I'd do this in Python would be to split the string into an array of characters, and remove the unnecessary elements, before putting the array back onto string form. But I can't figure out how to do that in Bash.
How do I remove the desired characters?
You can use Bash parameter substitution like this:
a="temp=53.0'C"
a=${a/*=/} # Remove everything up to and including = sign
a=${a/\'*/} # Remove single quote and everything after it
echo $a
53.0
Further examples are available here.
You could use sed with a regex which corresponds to the format of the string you want to be returned:
$ var="temp=53.0'C"
$ echo "$var" | sed -r 's/.*=([0-9][0-9]\.[0-9]).*/\1/g'
53.0
What exactly are the "rules" around what your original string looks like, and what the section to output looks like?
Same thing with BASH_REMATCH
> [[ $tmp =~ [0-9]+\.[0-9]+ ]] && echo ${BASH_REMATCH[0]}
53.0
Also agree with Josh but would improve the pattern match to consider the full range of floating point numbers.
.*=[ ]*([0-9]*\.[0-9]+)[cC].*
If you do not understand the pattern above, take the time to find out. Learning pattern matching will be one of the most useful things you ever do.
Test your pattern with something like http://www.freeformatter.com/regex-tester.html and then tailor for the platform you are using (e.g. Unix will probably need the brackets escaped with a backslash)
