unexpected operator/operand in Bourne script

ocicat · 07-28-2007, 05:15 PM

I'm still new to writing Bourne shell scripts, but the following has me stumped.

Code:

#!/bin/sh

s=/etc/X11/xinit

# find partition of directory
while [ `df | grep $s$` ]
do
    s=`dirname $s`
done

echo $s

Upon execution, I'm getting the error unexpected operator/operand. What am I missing?

Thanks.

macemoneta · 07-28-2007, 05:21 PM

while [ `df | grep $s$` ]

ocicat · 07-28-2007, 05:28 PM

Quote:

Originally Posted by macemoneta

while [ `df | grep $s$` ]

I thought the terminating '$' constrains the regular expression to match only at the end of the line. Is this wrong?

macemoneta · 07-28-2007, 05:39 PM

If that's what you want, then to insure proper evaluation use:

while [ `df | grep "${s}$"` ]

However, going one step further, you'll find that your command evaluates to a null string, which causes the while to fail.

Run this at the command line:

df

Do you see the string "/etc/X11/xinit" anywhere? What happens when the command evaluates to a null? You get:

while [ ]

ocicat · 07-28-2007, 05:44 PM

Quote:

Originally Posted by macemoneta

What happens when the command evaluates to a null? You get:

while [ ]

I was thinking that `df | grep ${s}$` would provide the return code from grep. Thanks for clearing that up.