bc utility is surely one of the underdogs when it comes to calculations on command line.
It’s a feature rich utility that has its own fan base but needs time to get comfortable with

• bc is included with (almost?) all Linux distros as standard, as well as (again, almost?) all Unices.
• Results from calculations in some proprietary flavours of bc have up to 99 decimal digits before and after the decimal point. This limit has been greatly surpassed in GNU bc. I don’t know what that limit is, but it’s at least many, many tens of thousands. Certainly it’s more than any GUI-based calculators (I’ve used) could accomodate.
• You may also find yourself working in an environment where you simply don’t have access to a GUI.
• The syntax for basic sums is almost identical to Google’s calculator function, so you can learn how to use two utilities in one go!

basename command in Kali Linux

Description
Basename is a simple command which returns the file name string without any path info and it is mostly used in shell scripts.
It can also remove the file extension, and return only the file name without an extension.
The syntax of basename command is as follows,
basename String [ Suffix ]
basename OPTION string – input string Suffix – string needs to be removed from the input
Options
-a, –multiple
support multiple arguments and treat each as a NAME.
-s, –suffix=SUFFIX
remove a trailing suffix SUFFIX, such as a file extension.
-z, –zero
separate output with NUL rather than a newline.
–help
display help information and exit.
–version
output version information and exit.
Examples
basename /usr/bin/sort
Outputs the string “sort”.
basename include/stdio.h .h
Outputs the string “stdio”.
basename -s .h include/stdio.h
Outputs the string “stdio”.
basename -a any/str1 any/str2
Outputs the string “str1” followed by the string “str2”.