I am trying to setup a regular expression to validate variables names. The rules are relatively simple, but I am no reg-ex jedi :)
it must start with a lettre or a underscore
[a-zA-Z_]
it can be followed by any repetition of letters or number, or dash "-" underscore "_" OR dot "."
[a-zA-Z_0-9\-\.]*
so far so good
[a-zA-Z_][a-zA-Z_0-9\-\.]*
BUT it may also include a number of repetition of this pattern \[\w+\]
this pattern, it like any of the other chars, it can appear any number of times, except at the first letter.
so I tried a few options such as
[a-zA-Z_][a-zA-Z_0-9\-\.]*(\[\w+\])*
or
[a-zA-Z_][a-zA-Z_0-9\-\.(\[\w+\])]*
I never got around to find the right syntax.
The idea is quite simple, it's a pattern, and it can located like any of the chars in the second sequence, one or more time, in any order
If this is not clear, see examples below
### valid examples
valid_var_name[a]
valid3_va[x].[y].name
valid_myVar[w].x
valide_myVar[a1].sub[b].SUB1_2[c].sub[d1].sub[d1].sub[d1].sub[d1].sub[d1].sub[d1].isValid
### invalid examples
2invalid // start with a number
.invalid // start with a dot
invalid[] // nothing between bracket
invalid].name // char ] alone is invalid
invalid[.]name // [.] dot is not a word
invalid[].name[1] // [] without a word not valid
^[a-zA-Z_]([\w\-.]|\[\w+\])*$
This starts with an alphabetic or underscore, then allows any sequence of either alphanumerics, -, ., or [name]
The anchors are needed so it won't match a variable in the middle of a string, like variable in 2variable.