This function returns the byte length and the character set of string, as well as the internal representation of the characters specified by start position start and length as length.
- The argument format specifies the format of the return value. There are four valid format-values:
- 8: Octal notation
- 10: Decimal notation (default)
- 16: Hexadecimal notation
- 17: ASCII characters are directly printed, multi-byte-characters are printed in hexadecimal format.
- The argument length specifies the maximal number of selected characters beginning at start position start. If length=0 all possible characters are selected. For negative numbers the absolute value of length will be used.
- The argument start specifies the start position of the character selection. If the character length of string is less than the absolute value of start the function returns NULL. For negative numbers the start position is set to the absolute value of start counted from the right (Default=1).
- If the argument string is NULL the function returns the character string 'NULL'.