Re: dumb escaping question when using Cygwin + NT commands

[Randall R Schulz <rrschulz at cris dot com>]

Scott,

At 15:15 2002-09-18, Scott Prive wrote:

> Hello,
>
> I get this odd problem when calling NT commands from Cygwin. I am 
> single-quoting the data, but the way I'm doing things (probably wrong...) 
> does not like passing $1 function arguments to NT commands. If I hardcode 
> the arguments internally, everything works.
>
> The two example functions below are intended to behave identical.
>
> #!/bin sh
>
> mount_drive () {
>    # Syntax: net 'use' '*' '\\redhat\foo' 'foo' '/user:foo'
>    net 'use' 'F:' '\\redhat\foo' 'foo' '/user:foo'
>
>    echo "The command returned $?"
>    return $?;
> }
Note that the status ($?) you're returning from the "mount_drive" shell 
procedure is that of the "echo" command, not that printed _by_ the echo 
command.

The only arguments in this example for which quoting changes the net 
argument passed to the underlying command is the one that includes "redhat" 
and the asterisk. The others contain no special characters requiring 
quoting or escaping to inhibit special interpretation.


> mount_drive2 () {
>    net '$1' '$2' '$3' '$4' '$5'
>    echo "we saw in mount_drive2: '$1' '$2' '$3' '$4' '$5' "
>
>    echo "The command returned $?"
>    return $?;
> }
The same "$?" issue exists here, of course.

You need to be aware of the difference between 'single quotes' and "double 
quotes." Variable expansion is inhibited in single-quoted arguments, but 
not in double-quoted ones. Furthermore, double quoted arguments protect 
single quotes, making the non-special. So you've probably confused yourself 
into thinking that in this example the "net" command saw the arguments you 
passed to the "mount_drive2" procedure. It did not. It saw arguments each 
consisting of a dollar sign followed by a digit. Then you echoed a single 
argument composed of some fixed text, some single quote marks and some 
expanded positional parameters.


> #
> mount_drive
> mount_drive2 'use' 'G:' '\\redhat\foo' 'foo' '/user:foo'
> ############# END SCRIPT
>
>
> the output I get from mount_drive2 is standard "usage info", indicating I 
> passed arguments incorrectly. However the debug echo *looks* correct.
>
> Someone please point out my mistake, else I'm doomed to some ugly hackish 
> workarounds ;-)
>
> Thanks,
>
> Scott

Randall Schulz
Mountain View, CA USA


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