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maybe a bug in bash?


From: Sebastian Luhnburg
Subject: maybe a bug in bash?
Date: Thu, 29 Jun 2023 11:55:12 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.11.0

Hello,

I'm sending this mail a past minutes ago, but I was not a member of this mailing list. The mail was not listed in the archive, so I send it again, with membership of the mailing list. I hope I don't sending it twice to you.


I'm not sure, if I found a bug or if I miss some understanding, but I want to report it, if it is a bug. Please tell me more, if I'm right or if it is my mistake.

I have a script, in which I have an password (I get it from a password manager - no excitement ;D ). The password begin with a $ and have an & in middle. I want to use this password in an here document, which inject some commands into a SSH-Connection (for simplification, I use the bash instead of ssh in the test script below). To use the password in the here document, I need to escape the special character. For this, I use printf. The echo command in the here document give me the right output. But if I run a subshell in the here document, the first \ for the $ is being cut away. But why? At the moment I think this is a bug. But if it is no bug, can you tell me why bash do this? My bash version is: 5.1.16(1)-release (x86_64-pc-linux-gnu) via Ubuntu 22.04.2 LTS.

You find a test script here:

#!/usr/bin/env bash

initial_password="\$abc&xyz"
echo "initial password: " $initial_password
printf -v password '%q' $initial_password
echo "initial password with escaped characters: " $password
bash << EOF
echo "password in here document: " ${password@Q}
/bin/bash -c "echo 'password in subshell in here document: ' ${password@Q}"
EOF


The output:


initial password:  $abc&xyz
initial password with escaped characters:  \$abc\&xyz
password in here document:  \$abc\&xyz
password in subshell in here document:  $abc\&xyz

Thank you very much!

Mit freundlichen Grüßen Sebastian Luhnburg IT ---------------------------------------------------------------------- swp software systems GmbH & Co. KG Königsbrücker Straße 124 01099 Dresden Tel: 0351-492850 Fax: 0351-4928550 www: https://www.vi-bim.de Kennen Sie schon unsere FAQ-Wissensdatenbank? Einfach hier klicken: https://faq.vi-bim.de Unsere Datenschutzerklärung finden Sie unter https://datenschutz.vi-bim.de Registergericht: Amtsgericht Dresden HRA 3008 persönlich haftender Gesellschafter: swp Beteiligungs GmbH Registergericht: Amtsgericht Dresden HRB 15 20 9 Geschäftsführer: Holger Schönemann, Stefan Urlberger

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