[ILUG] scripting question

[Brian Foster]

  | Date: Thu, 17 Feb 2011 12:41:43 -0000 (GMT)
  | From: "Ciaran Johnston" <cj at nologic.org>
  | 
  | Conor Wynne wrote:
  | > When scripting in bash, and using C style syntax, example
  | >
  | >    for (i=0;i<=50;i++)
  | >
  | > do I have to declare the variable(s) before hand?
  | 
  | I take it you mean declare "i" beforehand? No.

 However, the variable will be global (to the script).
 *IF* this is inside a function, that may not be want
 you want (and is arguably poor programming practice);
 in that case, declaring it ‘local’ is advisable:

    loop() {
        local -i i
        for ((i = 0; i <= 50; i++)) {
            ... do something ...
        }
    }

 Also, if the type is supposed to be constrained (as
 in this case) to an integer, declaring it as such
 (‘-i’) can help catch borks.  You can do that with
 globals(to the script) with ‘declare’.

 Incidentally, you can also use the sequence notation
 for loops such as the above:

        for i in {0..50}; do
            ... do something ...
        done

 I'm uncertain how much of the above is specific to
 GNU bash(1), and how much is in POSIX.  (Functions
 are in POSIX.)

cheers!
	-blf-

  |                                                The syntax is double
  | brackets, not single brackets, unless I'm mistaken:
  | 
  | for (( i = 0; i <= 50; i++ )) ; do
  |     echo $i
  | done
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