Bash – scp, globbing, and different shells

bashshellsshwildcardszsh

The other day at work I tried doing

scp remotehost:~/*.txt .

and I received an error about the *, *.txt file not found sorry, not at work and I forget the exact error

on my workstation I run zsh 4.3. on the remotehost bash is the default shell, and the version of zsh is older (4.2 vs 4.3) on that. I then tried switching to bash on my workstation, and doing the exact same command. This time it worked. What is the root 'cause of this. Is there anyway to do globbing, or wildcards between these 2 systems (without switching to bash)?

Best Answer

zsh's behavior is a little different here than most other shells. Other shells, like bash, try to expand the wildcards. If they cannot expand to anything they pass the literal string (containing the wildcards) to the application instead. But zsh does not do that (well, there is an option for that, to do it or not). The zsh will print that error and not perform the command. You can override that by escaping the wildcard, if you really want it passed to the application. In this case you do since you want the other side shell to expand it. So use:

scp remotehost:\*.txt .

This is actually the correct behavior, since if you did have some local *.txt files in your home they would be expanded to a name that might not exist on the remote. That's not what you want.

Related Solutions

Bash and Zsh – Make `rm` Interactive with Globbing

It's not easy. The problem is that when you do:

rm -- *.txt

rm just sees the list of files, not the globbing pattern which has already been expanded by the shell.

What you could do is (zsh):

alias rm='noglob rm'

This tells zsh that patterns should not be expanded when calling rm. Then you can redefine rm as a function that does the expansion itself and adds the "-i" if need be something like:

'rm'() {
  [[ "$*" = *[*[?]* ]] && set -- -i "$@"
  command rm $~@
}

The problem with that approach though is that this new "rm" doesn't see the difference between

rm *

and

rm '*'

To remove the file called *, you'd have to write it:

rm [*]

Bash – find and globbing (and wildcards)

Both the find command and the shell are capable of file globbing.

This is unusual - most commands are NOT capable of globbing and rely entirely on the shell to expand globs. But find is a super duper mega power user tool that you can very easily hurt yourself with!

Example: when you do the command

   find /path -iname *.txt

The first thing that happens is the shell attempts to find all files that match *.txt in the current directory. If it finds any, it substitutes the names of all the matching files for the glob, and then calls the find command. The find command never sees the glob if this happens, the shell has expanded it out of existence.

But if there are no files in the current directory that match the glob, the shell shrugs its metaphorical shoulders and passes the glob unchanged to find. So at that point, the find command (which understands globs, remember) will output the names of all files it finds under /path that match the glob.

So using globs this way means that find will behave differently depending on the content of the current directory. This is almost certainly not what you want!

To prevent the shell from tampering with globs before find sees them, escape the globs with appropriate shell metacharacter quoting. Usually this just means putting your globstrings in single quotes like this

   find /path -iname '*.txt'

Remember, GLOBS ARE NOT REGEXES - the glob ".*" and the regex ".*" are very different and do not match the same strings!

Best Answer

Related Solutions

Bash and Zsh – Make `rm` Interactive with Globbing

Bash – find and globbing (and wildcards)

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