Parsing, metacharacters, tokens.

[Cristian Zoicas]

Hello all,

There are situations when it is not clear from the manual how bash
performs expansions/splitting/substitutions.

According to what is written in the manual a metacharacter is:

    A character that, when unquoted, separates words. A metacharacter
    is one of the following characters:
        <space> <tab> <newline> | & ; ( ) < >

Now let's assume the following statement:

A=START$(echo _)END

According to the definition of metacharacters the first token would be
"A=START$" (because '(' separates tokens) and then will follow the rest of
the tokens .

I may be wrong, but I my intuition tells me that bash does something like
this: The only token found on that line is the entire line itself. If this
is true, then '(' does not behave like a metacharacter because it does not
separate words due to that fact that it is preceded by a $. So there seems
to be some kind of entity in bash that is a metasequence ('$(' in this
case) which is interpreted as a metasequence only when the value of A is
computed but it is not considered a metasequence when the line is read.

Can you explain what is going on?

Best regards
Cristian