By using brackets, you can limit the valid characters in a format specification.
This specification... |
...means this |
| N[1357] | One digit: 1, 3, 5, or 7. |
| N[1357](3) | Three digits, each of which can be 1, 3, 5, or 7. |
| X[#]N[4] | A "#" character and then 4. |
| X[AaBb] | One character: A, a, B, or b. |
An exclusion symbol, "^", is available to disallow invalid characters. In order to disallow characters, the "^" symbol must be in the first position of the string. All characters following the "^" are disallowed.
If the "^" is not at the beginning of the string, then "^" is a valid character.
When using the exclusion symbol in combination with a hyphen (-), the hyphen must be the last character before the closing bracket (]).
| A[^QVZ] | Any letter of the alphabet except Q, V, or Z. |
| X[^*](2-4) | Two to four characters; not an asterisk. |
| X[ #<^] | One of three possible characters: "#", "<", or "^". |
| X[ #<^135] | One of six possible characters: "#", "<", "^", 1, 3, or 5. |
| X[ #<^^] | An invalid specification. |
| X[^_*#-](3-25) | Three to twenty five characters but not "_", "*", "#", or "-". |
| X[^_-*#](3-25) | An invalid specification, because the hyphen (-) is not the last character before the closing bracket. |