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

version graph

Package: dash; Maintainer for dash is Andrej Shadura <[email protected]>; Source for dash is src:dash (PTS, buildd, popcon).

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

Date: Mon, 16 Aug 2010 14:42:01 UTC

Severity: wishlist

Tags: upstream, wontfix

Merged with 538100, 550399, 599834, 652509, 698593

Found in versions 0.5.5.1-7.4ubuntu1, dash/0.5.4-12, dash/0.5.5.1-2, dash/0.5.5.1-6, dash/0.5.5.1-7.4

Full log

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Date: Mon, 16 Aug 2010 15:30:35 -0500
From: Jonathan Nieder <[email protected]>
To: "Alexander E. Patrakov" <[email protected]>
Cc: [email protected]
Subject: Re: Bug#593237: dash: Can't echo \b
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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

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