[protomikron]

Some nice stuff, but also some stuff, where things get easier if you just switch to a language with less caveats (like Python).

My rule of thumb is to use Bash to write simple scripts, if they fit on the command line and have just one level of loop or if-else (lines can get very long, though ...). However for more complicated stuff I use the alternative programs (find, sed, awk, ...), as they behave more predictable.

Furthermore I am not sure one should use such simplified versions, that are just wrong:

    is_float() {
        # Usage: is_float "number"

        # The test checks to see that the input contains
        # a '.'. This filters out whole numbers.
        [ -z "${1##*.*}" ] &&
            printf %f "$1" >/dev/null 2>&1
    }

I mean having a '.' in the string does make it a non-integer, but what about other floats like 2e3?

[tlamponi]

  > where things get easier if you just switch to a language with less caveats (like Python).

For general, non-domain specific things, it gets IMO easier by two main reasons 1) obviously when using tools where one has more experience with, but 2) also when the tool is more widely available, and POSIX shell is probably one of the most (by default) available interpreters with a somewhat human-friendly input mode there is. I know if I write a script or some functions in POSIX shell I can copy it and run it wherever I want (besides Windows, but don't really know anybody close to me that still uses that, especially in a server environment). Sure, if everywhere you want to run it python/perl/... is just available, or simple to install (i.e., any modern Linux or *BSD distro), then the second point hasn't that much weight anymore besides maybe for minimal Alpine Linux CTs (< 8 MB for a full fledged distro!).

  >  I mean having a '.' in the string does make it a non-integer, but what about other floats like 2e3?

They use the printf "%f" float format conversion so `printf "%f" 2e3` will work just fine, whereas using something that definitively is not a float makes printf exit with an error code as it fails to format the value as float, failing this check.

[protomikron]

> They use the printf "%f" float format conversion so `printf "%f" 2e3` will work just fine, whereas using something that definitively is not a float makes printf exit with an error code as it fails to format the value as float, failing this check.

You are of course correct (sorry to sound like a language model), I missed the printf.

[hddqsb]

Actually, the function returns success if the input contains "." and printf succeeds, so it does not consider 2e3 to be a float. I agree that this function is odd (it's not even useful for identifying simple numbers of the form "123.456", because it considers 2.0e3 to be a float).