Bash Scripting

Extracting / Parsing Filenames

Use the basename to extract filenames from a path and and dirname to extract the path of a filename.

Eg:

dirname /etc/hosts
/etc

basename /etc/hosts
hosts

To extract only the extension or the filename without the extension, use bash's string matching:

Filename=$(basename /etc/resolv.conf)
Ext="${Filename##*.}"
Name="${Filename%.*}"

Arithmetic Operations

Do integer arithmetic operations on variables within double brackets. For example:

Value=1
ValuePlusOne=$((Value + 1))
ValueTimes12=$((Value * 12))

The operators that are supported are:

+ - / * % 

Bitwise operators also work:

^ (XOR)   | (OR)   & (AND)