_Added in 1.9.0_

*$mkfn(filename)*

Replaces invalid filename characters with underscore.

*Parameters*

table(ktable).
|*Parameter*|*Description*|
| filename | The filename to format. |

*Example*

<pre>
; Format the filename 'tes\t.txt' to 'tes_t.txt'
//echo -ag $mkfn(tes\t.txt)
</pre>