Hi

i was going through the script debugging technique. below example was given in the book.

1   #!/bin/sh
     2
     3   Failed() {
     4   if [ $1 -ne 0 ] ; then
     5   echo "Failed. Exiting." ; exit 1 ;
     6   fi
     7   echo "Done."
     8   }
     9
    10   echo "Deleting old backups, please wait... \c"
    11   rm -r backup > /dev/null 2>&1
    12   Failed $?
    13
    14   echo "Make backup (y/n)? \c"
    15   read RESPONSE
    16   case $RESPONSE in
    17   [yY]|[Yy][Ee][Ss]|*)
    18   echo "Making backup, please wait... \c"
    19   cp -r docs backup
    20   Failed
    21   [nN]|[Nn][Oo])
    22   echo "Backup Skipped." ;;
    23  esac

[nN]|[Nn][Oo]) ./buggy2.sh: syntax error at line 21: ')'
unexpected

./debug6: 21: Syntax error: ")" unexpected (expecting ";;")

Failed ;;

That is simply a matter of syntax of the case statement. By the way this:

[yY]|[Yy][Ee][Ss]|*)

*)

Hi Scrutinizer

the code is working.

[yY]|[Yy][Ee][Ss]|*)

my question is why i need to use 2 colon after Failed not one?
also how does author know just by seeing one single line(means by seeing o/p of debug) that he need to put 2 colon after Failed.

Sure it is working, it is just that it is wrong. Whatever you input, it will be interpreted as "yes".

Your first question I answered.

The author sees that the shell is not expecting to see a ")" character and the author concludes that this is due to the fact that the previous part was not closed with ;; , which is a matter of syntax.

That's two semi-colons and not colons.

Because that's the syntax for terminating a block of case statements. The first semi-colon ends that particular statement and the second ends the whole case block. The second one ensures that you don't try the following case blocks.

It is also possible to try the following block/s if you replace the second semi-colon with an ampersand (I think that's called a fall-through).

var='THE UNIX AND LINUX FORUMS';

case "$var" in

 *UNIX*)   echo "Has UNIX";&

 *LINUX*)  echo "Has LINUX";;

 *FORUMS*) echo "HAS FORUMS";;

esac

Has UNIX
Has LINUX

;& is bash 4.0. The OP states #!/bin/sh

Oops, I didn't see the shebang line. By the way, it's not bash-specific; also works in ksh88/93.