Debian Bug report logs - #593237
dash built-in echo expands \nnn sequences

Reply or subscribe to this bug.

Display info messages

Message #5 received at [email protected] (full text, mbox, reply):

From: "Alexander E. Patrakov" <[email protected]>

To: [email protected]

Subject: dash: Can't echo \b

Date: Mon, 16 Aug 2010 20:38:57 +0600

Package: dash
Version: 0.5.5.1-6
Severity: normal

There seems to be no way to produce the sequence "\b" (that's
backslash, then the letter b) using dash's builtin echo. Bash
and /bin/echo work fine. I have tried the following commands in my
shell script:

echo "\b"
echo '\b'

...but they only produce a backspace character (0x08) even though
I have not passed the -e switch.

-- System Information:
Debian Release: squeeze/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.32-5-amd64 (SMP w/2 CPU cores)
Locale: LANG=ru_RU.UTF-8, LC_CTYPE=ru_RU.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages dash depends on:
ii  debianutils                   3.2.3      Miscellaneous utilities
specific t
ii  dpkg                          1.15.7.2   Debian package management
system
ii  libc6                         2.11.2-2   Embedded GNU C Library:
Shared lib

dash recommends no packages.

dash suggests no packages.

-- debconf information:
* dash/sh: true

-- 
Alexander E. Patrakov

Message #10 received at [email protected] (full text, mbox, reply):

From: Jonathan Nieder <[email protected]>

To: "Alexander E. Patrakov" <[email protected]>

Cc: [email protected]

Subject: Re: Bug#593237: dash: Can't echo \b

Date: Mon, 16 Aug 2010 15:30:35 -0500

forcemerge 550399 593237
quit

Hi,

Alexander E. Patrakov wrote:

> There seems to be no way to produce the sequence "\b" (that's
> backslash, then the letter b) using dash's builtin echo. Bash
> and /bin/echo work fine. I have tried the following commands in my
> shell script:
> 
> echo "\b"
> echo '\b'
> 
> ...but they only produce a backspace character (0x08) even though
> I have not passed the -e switch.

Indeed, echo is not guaranteed to do that[1].  The Almquist shell that
dash is based on never supported the -e switch.  Changing this
historical behavior would be a big pain.

Portable shell scripts should use

	printf '%s\n' '\b'

and unportable scripts should use

	#!/bin/bash

or similar.

Hope that helps,
Jonathan

[1] http://www.opengroup.org/onlinepubs/9699919799/utilities/echo.html

Send a report that this bug log contains spam.