#### Remove leading 0's
This uses extended globbing. More of that [http://mywiki.wooledge.org/glob#extglob here]. Also see BashExtendedGlobs. To enable this:
```plaintext
shopt -s extglob
```
and then
```plaintext
A="00123"
B=${A##+(0)}    # B := 123
```
Here the `##` means remove longest match, and `+(0)` means match 1 or more 0's.

Related example:
```plaintext
A="abababacde"
B="${A##+(ab)}"     # B := acde
```