Shell Programming and Scripting

Hi All

I have a csh shell script which should check if a given file is a zip file as below:

****************************************
#!/bin/csh -f

if [[ "`echo ${1} | cut -d'.' -f2`" = "zip" ]]; then
echo is a zip file
else
echo sorry not a zip file
endif
exit
****************************************

but when I run this I get "missing ]" not sure where there is a missing ]

Please help

Thanks
Raj

Code:

#!/bin/csh

if ( "`echo ${1} | cut -d'.' -f2`" == "zip" )  then
  echo $1 is a zip file
else
  echo sorry, $1 is not a zip file
endif