Date: Thu, 16 Mar 2017 23:06:14 -0400
From: Wayne Pollock <profwaynepoll...@gmail.com>
Message-ID: <b5b540ef-3de8-474d-ba4c-bfd093170...@gmail.com>
| echo "\$ foo"
| produce:
| $ foo
Yes.
| \$ foo
No.
| The <backslash> shall retain its special meaning as
| an escape character (see Escape Character (Backslash))
| only when followed by one of the following characters
| when considered special:
"considered special" is a magic term, not just "happens to expand
to something" - whether a character is special or not depends
upon the context in which the examination is made, and not at
all on what happens to be in the string. That "$ " expands
to "$ " rather than something else is immaterial, the '\' causes
the '$' to be just a boring non-entity characted, so that the
character that follows it is not examined for a $ expansion at
all. It happens (and must happen) in that order, we cannot look
at what comes after the '$' to see if the '$' is an expanding $
or not.
For example the text inside $(( )) is treated as a double quoted
string, except that the " character is not "considered special"
in that string. That means that \" is not needed to embed a
literal " in that kind of string (not that doing so would be useful).
A similar thing applies in the case of here documents (with unquoted
<<term so expansions happen - a case in which " characters are much
more likely to occur. '$' characters, and ` (etc) are "considered
special" in both those cases.)
| A related question is what happens if a dollar-sign is
| the last character
But yes, that one is a good point, "end of input" should be
treated the same as space, newline, etc. At the minute what
happens to a '$' that is not followed by anything is unspecified
(in the literal sense - the text only talks about what happens
when the 'following char' is ... and says nothing at all about
what happens when there is no following char.)
That should be fixed, so this (new) wording ...
If a '$' that is neither within single-quotes nor escaped by a <backslash>
is immediately followed by a character that is not a <space>, not a <tab>,
not a <newline>, and is not one of the following:
[...]
the result is unspecified. If a '$' that is neither within single-quotes nor
escaped by a <backslash> is immediately followed by a <space>, <tab>,
or a <newline>, the '$' shall be treated as a literal character.
should instead be ...
If a '$' that is neither within single-quotes nor escaped by a <backslash>
is immediately followed by a character that is not a <space>, not a <tab>,
not a <newline>, and is not one of the following:
[...]
the result is unspecified. If a '$' that is neither within single-quotes nor
escaped by a <backslash> is immediately followed by a <space>, <tab>,
or a <newline>, or is not followed by any character, the '$' shall be
treated as a literal character.
kre
