Write Access
Write Access
Bash 4 Compatibility
Your article on the new Bash version 4.0 (August 2009, pg. 62) refers to the topic of compatibility right at the start, pointing to eight changes introduced for the sake of POSIX compatibility. Chet Ramey also seems to have been referring to this in your interview, when he said that the new version was as downwardly compatible as possible, but version 3.2's behavior was just incorrect in some places.
In version 4.0 of the shell, the $@ and $* parameter lists are fairly inconsistent "semi-variables" (bash -uc 'echo $@' "$@:unbound variable"; but: @=1 @=1: command not found), although this is not mentioned in the COMPAT file.
These changes mark a departure of the new shell from the POSIX standard, which clearly states: "If there are no positional parameters, the expansion of '@' shall generate zero fields [...]."
Bash 4 simply treats $@ and $* as "undefined" if no parameters have been passed in. This problem primarily occurs when the nounset option (-u) is used to protect against the use of undefined variables and thus make scripts more secure and robust. In this light, the problem might only affect a couple of programmers, as most people still unfortunately work without nounset. (-u is not even mentioned in the Bash manpage.) However, it is quite conceivable that this new behavior could cause other problems that are still waiting to be discovered.
In my opinion, these changes are a careless step backwards and do not indicate the kind of diligence in release management you would expect from a critical package like Bash. This is the reason why I declared the changes to be a grave bug on the following Debian bug report site: http://bugs.debian.org/519165
Martin F Krafft
LM
Bernard Bablok, the author of the Bash 4 article, writes:
I am not familiar with the particular issue described in this letter, but I will assume that Martin Krafft is right. Even so, I cannot share his assessment of Bash 4 as a "careless step backwards." In a complex program such as Bash, it can happen that a compatibility issue or an unwanted problem creeps in. There are bug lists and mailing lists in order to clarify or change such things.
Thanks for your letter. We'll hope the bug report you filed with Debian will draw some attention to this issue.
ECIS and EC
Contrary to an article in your magazine (see "Microsoft's Anticompetitive Behavior" July 2009, pg. 10), ECIS is not part of the European Commission.
They are a lobby group.
Could you please print a correction and amend the online version?
Jonathan Todd European Commission Spokesman on Competition
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
New Slimbook EVO with Raw AMD Ryzen Power
If you're looking for serious power in a 14" ultrabook that is powered by Linux, Slimbook has just the thing for you.
-
The Gnome Foundation Struggling to Stay Afloat
The foundation behind the Gnome desktop environment is having to go through some serious belt-tightening due to continued financial problems.
-
Thousands of Linux Servers Infected with Stealth Malware Since 2021
Perfctl is capable of remaining undetected, which makes it dangerous and hard to mitigate.
-
Halcyon Creates Anti-Ransomware Protection for Linux
As more Linux systems are targeted by ransomware, Halcyon is stepping up its protection.
-
Valve and Arch Linux Announce Collaboration
Valve and Arch have come together for two projects that will have a serious impact on the Linux distribution.
-
Hacker Successfully Runs Linux on a CPU from the Early ‘70s
From the office of "Look what I can do," Dmitry Grinberg was able to get Linux running on a processor that was created in 1971.
-
OSI and LPI Form Strategic Alliance
With a goal of strengthening Linux and open source communities, this new alliance aims to nurture the growth of more highly skilled professionals.
-
Fedora 41 Beta Available with Some Interesting Additions
If you're a Fedora fan, you'll be excited to hear the beta version of the latest release is now available for testing and includes plenty of updates.
-
AlmaLinux Unveils New Hardware Certification Process
The AlmaLinux Hardware Certification Program run by the Certification Special Interest Group (SIG) aims to ensure seamless compatibility between AlmaLinux and a wide range of hardware configurations.
-
Wind River Introduces eLxr Pro Linux Solution
eLxr Pro offers an end-to-end Linux solution backed by expert commercial support.