bash skills

In this paper some of the major record bash syntax, notes

1. hexadecimal conversion

$ echo $(( 2#11 ))
3
$ echo $(( 16#1E ))
30

Upcoming specified hexadecimal number into decimal, such as the above is a hexadecimal number 1E converted to decimal, so the result is 30.

2. Check the value of the variable number of characters

$ a="Hello world"; echo ${#a}
11

Reference: bash formula