[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
bug#14299: Incorrect output of `printf "\\n"`
From: |
Eric Blake |
Subject: |
bug#14299: Incorrect output of `printf "\\n"` |
Date: |
Mon, 29 Apr 2013 09:42:00 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130402 Thunderbird/17.0.5 |
tag 14299 notabug
thanks
On 04/28/2013 12:44 PM, Pavel Elkind wrote:
> Dear developers,
>
> I found the following potential bug in printf (version 8.17).
>
> Actual result:
> `printf "\\n"` prints a newline caracter.
Of course. That's what POSIX requires it to print.
$ set -x
$ printf ".\\n."
+ printf '.\n.'
.
.
$ set -
>
> Expected result:
> `printf "\\n"` prints a sequence of two individual characters, '\' and 'n',
> like '\n', but not a newline character.
If you want printf to print a literal backslash, you have to properly
escape it. There are two levels of escaping to consider; shell escaping
(before printf ever sees its argv), and printf escaping. You missed a
level, because you forgot that within "", the shell converts \\ into a
literal \ as part of the argv, and as my 'set -x' trace showed above,
you were passing only one backslash, not two, to printf. Within printf,
when it sees the single backslash-n sequence, it converts that escape
sequence to newline.
You probably meant to do any one of these equivalent actions:
printf '.\\n.'
printf .\\\\n.
printf ".\\\\n."
all of which result in the argv handed to printf still containing two
backslashes.
As such, I'm closing this as not a bug, although you may continue to
reply here if you have further comments.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
signature.asc
Description: OpenPGP digital signature