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I am planning on filing a bug on coreutils for this, as this behavior is unexpected, and there isn't any practical use for it in the real world... Although it did make me chuckle at first, as I never even knew one could create files with wildcard in their filename. How practical is a filename with a wildcard in it? Who even uses such a feature?

I recently ran a bash command similar to this:

ln -s ../../avatars/* ./

Unfortunately, I did not add the correct amount of "../", so rather than providing me with an informative error, it merely creates a link to a "*" file which does not exist. I would expect this to do that:

ln -s "../../avatars/*" ./

As this is the proper way to address such a filename.

Before a submit a bug on coreutils, I would like the opinion of others. Is there any practical use for this behavior, or should ln provide a meaningful error message?

And yes, I know one can just link to the entire directory, rather than each file within, but I do not wish newly created files to be replicated to the old location. There are only a few files in there that are being linked right now.

Some might even say that using a wildcard in symlinking is bad practice. However, I know the contents of the directory exactly, and this is much quicker than manually doing each file manually.

kveroneau
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1 Answers1

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This isn't a bug.

In the shell, if you use a wildcard pattern that doesn't match anything, then the pattern isn't substituted. For example, if you do this:

echo *.c

If you have no .c files in the current directory, it will just print "*.c". If there are .c files in the current directory, then *.c will be replaced with that list.

For many commands, if you specify files that don't exist it is an error, and you get a message that seems to make sense, like "cannot access *.c". But for ln -s, since it is a symbolic link, the actual file doesn't have to exist, and it goes ahead and makes the link.

Vaughn Cato
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  • Yes, and this behavior is actually mandated by POSIX: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_13_03 – Nemo Aug 20 '12 at 04:40
  • Thank you for the clarification on this. I never ran into this before. I normally tab-complete everything, but when I did this, I created a new directory, entered the directory, and used my bash history to run the command, which obviously was no longer pointing to the correct relative directory. Lesson learned. – kveroneau Aug 20 '12 at 04:48
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    Though not in _every_ shell. Eg. zsh has it configurable and will by default print an error for a pattern that matches nothing. – Michał Politowski Aug 20 '12 at 05:46
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    with bash too, just add `shopt -s failglob` in ~/.bashrc – Nahuel Fouilleul Aug 20 '12 at 07:12