conditional execution

tostay2003 · 12-27-2007, 03:18 PM

I want to execute two statements if my variable _Validity is false if true none of them should be executed.

But the exit 1 in below code is executed regardless of value in _Validity. Echo statement works appropriately.

Code:

$_Validity=/sbin/false
$_Validity || echo "Invalid variable"; exit 1

I have tried to enclose these two statments in braces

Code:

$_Validity ||  { echo "Invalid variable"; exit 1 }

but I get the following error

Quote:

{ Not found

FYI : I am using ksh

David1357 · 12-27-2007, 04:25 PM

Quote:

Originally Posted by tostay2003

Code:

$_Validity=/sbin/false
$_Validity || echo "Invalid variable"; exit 1

That semi-colon before "exit 1" tells the interpreter that it is the end of the command. So exit 1 will alway be executed unless someone else exits.

You could try

Code:

$_Validity=/sbin/false
$_Validity || echo "Invalid variable" && exit 1

but I'm not sure how the operator precedence works out.

ghostdog74 · 12-27-2007, 10:17 PM

Quote:

Originally Posted by tostay2003

Code:

$_Validity=/sbin/false
$_Validity || echo "Invalid variable"; exit 1

keep it simple

Code:

if [ $_Validity equal something ];then
  ...do something
else
  .... do other things
  exit
fi

tostay2003 · 12-28-2007, 07:45 AM

David 1357

Quote:

$_Validity || echo "Invalid variable" && exit 1

This statement is behaving like if ... else i.e. if true then exit 1, if false then execute the echo statement.

ghostdog74

Quote:

keep it simple

Code:
if [ $_Validity equal something ];then
...do something
else
.... do other things
exit
fi

In addition to making the scripts work. I am trying to learn scripting as well. That is the reason for using that sort of things. I read somewhere that if I put those in braces it will work , but its giving an error.

ghostdog74 · 12-28-2007, 10:22 AM

Quote:

Originally Posted by tostay2003

I am trying to learn scripting as well.

yes, and learn it the proper way. Learn to make your code more readable and scalable. There's nothing wrong writing it that way , however if you are to add in more conditions later you might have a problem. Anyway, its up to you.

David1357 · 12-28-2007, 03:01 PM

Quote:

Originally Posted by tostay2003

This statement is behaving like if ... else i.e. if true then exit 1, if false then execute the echo statement.

That is what I meant about not knowing how the operator precedence would work out.

Reading the man page for ksh says that

Code:

_Validity=/bin/false
$_Validity ||  { echo "Invalid variable"; exit 1 ;}

should work. I just tested it here. You have to put the trailing "}" right after a ";".