From: Chris Johnson <cjohnson@cs.utk.edu>
To: DervishD <zsh@dervishd.net>, Zsh Users <zsh-users@sunsite.dk>
Subject: Re: Printing square brackets and backslashes
Date: Sun, 23 Oct 2005 20:30:33 -0400 [thread overview]
Message-ID: <20051024003033.GA2835@namib.cs.utk.edu> (raw)
In-Reply-To: <20051024000408.GA1124@DervishD>
DervishD sent me the following 0.9K:
> > Hi all :)
> >
> > $ print \[\\\]
> > []
> > $ /bin/echo -e \[\\\]
> > [\]
> > $ print -r \[\\\]
> > [\]
> > $ print \\
> > \
>
> I can understand the first case, but I don't understand the last
> one: in the first case, what I misunderstood is that the shell quotes
> the chars, producing "[\]" and "print" prints them, interpreting some
> escape directives: "[]". But in the last case, nothing should then be
> printed, because zsh quotes the backslash and "print" gets a single
> backslash, that is, an empty escape directive that shouldn't print
> anything :? Is "print" assuming that a single backslash is not an
> empty escape directive? Is a single, isolated backslash a synonim for
> "\\"?
This is in the zsh user's guide at:
http://zsh.sourceforge.net/Guide/zshguide03.html#l32
Look under section 3.2.1, Builtins for printing.
# --------------------------------------------------------------------
Secondly, those backslashes can land you in real quoting difficulties.
Normally a backslash on the command line escapes the next character ---
this is a different form of escaping to print's --- so
print \n
doesn't produce a newline, it just prints out an `n'. So you need to
quote that. This means
print \\
passes a single backslash to quote, and
print \\n
or
print '\n'
prints a newline (followed by the extra one that's usually there). To
print a real backslash, you would thus need
print \\\\
Actually, you can get away with the two if there's nothing else after
--- print just shrugs its shoulders and outputs what it's been given ---
but that's not a good habit to get into.
--
Chris Johnson
cjohnson@cs.utk.edu
http://www.cs.utk.edu/~cjohnson
next prev parent reply other threads:[~2005-10-24 0:30 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-23 21:43 DervishD
2005-10-24 0:04 ` DervishD
2005-10-24 0:30 ` Chris Johnson [this message]
2005-10-24 8:16 ` DervishD
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