SPRINTF — Formats a string
Formats a variable or set of variables according to a format string.
The most common case for the use of SPRINTF is to zero-pad a number to a certain length:
; Returns 00123
exten => 123,1,Set(padfive=${SPRINTF(%05d,${EXTEN})})
Most of the format options listed in the manpage for sprintf(3)
are also implemented in this
dialplan function.