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Re: echo builtin doesn't handle end-of-options flag

From: Eric Blake
Subject: Re: echo builtin doesn't handle end-of-options flag
Date: Sun, 16 Aug 2020 11:30:59 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 8/16/20 11:20 AM, Eli Schwartz wrote:


echo does not accept options, and is not permitted to accept options
including "--".

bash does accept -n, -e, -E in violation of POSIX, unless shopt -s shopt
-s xpg_echo is set, but it doesn't implement -- and I don't really see a
justification to do so.

Not quite: https://www.austingroupbugs.net/view.php?id=1222 says that accepting -e and -E will become acceptable in the next revision of POSIX (accepting -n was already acceptable on non-XSI systems).

Either enable xpg_echo or use printf.

POSIX recommends using printf. My personal recommendation is to avoid xpg_echo except when trying to break things - there are a number of what claim to be bash scripts that are not aware of the effects of xpg_echo and which operate incorrectly when you actually set it; whereas using printf is reliably portable.

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

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