From: Bart Schaefer <schaefer@brasslantern.com>
To: Derek Peschel <dpeschel@eskimo.com>
Cc: zsh-workers@sunsite.dk
Subject: Re: BUG? - 4.0.2 - parameter substitution won't double backslashes in values
Date: Thu, 7 Feb 2002 21:00:05 +0000 (GMT) [thread overview]
Message-ID: <Pine.BSF.4.40.0202072033570.37987-100000@brasslantern.com> (raw)
In-Reply-To: <20020207122222.A14893@eskimo.eskimo.com>
On Thu, 7 Feb 2002, Derek Peschel wrote:
> Maybe my explanation was too complicated, or probably you missed the
> beginning of the thread.
I saw the beginning of the thread, and I saw Sven's answer, which didn't
seem to bear repeating, so I was responding only to the parenthetical
comment about backspace changing to "\b". As Sven's answer apparently
does bear repeating:
> I have a string containing the characters "a", backslash, "b", "c".
[...]
> I want to use parameter substitution to convert the backslash to two
> backslashes.
You *probably* want the (q) parameter flag:
zsh% x='a\bc'
zsh% print ${(q)x}
a\bc
zsh% print -r ${(q)x}
a\\bc
However, (q) will also insert a backslash in front of any other character
that is special to the shell parser. If you want *only* to double all the
backslashes, you need one of:
zsh% print -r ${x//\\\/\\\\}
a\\bc
zsh% print -r ${x:gs/\\/\\\\\\\\}
a\\bc
The reason you need three backslashes as the pattern in the first case is
rather complicated and could possibly be considered a bug; it has to do
with using glob-pattern interpretation in ${x//...}. The reason you need
eight backslashes as the replacement in the second case is a lot easier to
explain; the eight are reduced to four by the initial parse of the shell
command line, and then reduced again to two when the :gs replacement
occurs.
The second one is probably more reliable, as it works the same even if the
expansion is enclosed in double quotes.
next prev parent reply other threads:[~2002-02-07 21:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-07 4:39 Derek Peschel
2002-02-07 10:33 ` Peter Stephenson
2002-02-07 13:19 ` Derek Peschel
2002-02-07 19:20 ` Bart Schaefer
2002-02-07 20:22 ` Derek Peschel
2002-02-07 21:00 ` Bart Schaefer [this message]
2002-02-08 9:29 ` Derek Peschel
2002-02-08 21:35 ` Bart Schaefer
2002-02-07 10:44 ` BUG? - 4.0.2 - " Sven Wischnowsky
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