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Full Discussion: Best practice for bracket comparisons?
Top Forums Shell Programming and Scripting Best practice for bracket comparisons? Post 302386503 by jim mcnamara on Tuesday 12th of January 2010 03:07:32 PM
Old 01-12-2010
Several points: [[ and [ may not have precisely the same semantics in some shells. example ksh.
try
Code:
type [  
type [[

Comparisons with string values are [ "string" = "string" ], not ==.

anyway - don't hard code values, except perhaps something that will never change,
example: a status return code of zero always means 'ok', so it can never change.

Why do this? because you can put all of the control variables right at the top of the code, so you can change behavior just by editing a few closely located lines of code. The other reason is that you could miss a "1" somewhere during an edit, completely breaking your code.

A lot of code examples on the forums here do not follow that practice because adding extra variables confuses people just starting out in scripting.
 

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LEARN ABOUT OPENDARWIN

return

return(n)						       Tcl Built-In Commands							 return(n)

__________________________________________________________________________________________________________________________________________________

NAME

       return - Return from a procedure

SYNOPSIS

       return ?-code code? ?-errorinfo info? ?-errorcode code? ?string?
_________________________________________________________________

DESCRIPTION

       Return  immediately from the current procedure (or top-level command or source command), with string as the return value.  If string is not
       specified then an empty string will be returned as result.

EXCEPTIONAL RETURNS

       In the usual case where the -code option isn't specified the procedure will return normally (its completion code will be TCL_OK).  However,
       the -code option may be used to generate an exceptional return from the procedure.  Code may have any of the following values:

       ok	 Normal return:  same as if the option is omitted.

       error	 Error	return:  same as if the error command were used to terminate the procedure, except for handling of errorInfo and errorCode
		 variables (see below).

       return	 The current procedure will return with a completion code of TCL_RETURN, so that the procedure that invoked it will return also.

       break	 The current procedure will return with a completion code of TCL_BREAK, which will terminate the innermost nested loop in the code
		 that invoked the current procedure.

       continue  The  current  procedure  will	return	with  a completion code of TCL_CONTINUE, which will terminate the current iteration of the
		 innermost nested loop in the code that invoked the current procedure.

       value	 Value must be an integer;  it will be returned as the completion code for the current procedure.

       The -code option is rarely used.  It is provided so that procedures that implement new control structures can  reflect  exceptional  condi-
       tions back to their callers.

       Two  additional	options, -errorinfo and -errorcode, may be used to provide additional information during error returns.  These options are
       ignored unless code is error.

       The -errorinfo option specifies an initial stack trace for the errorInfo variable;  if it is not specified then the  stack  trace  left	in
       errorInfo  will	include the call to the procedure and higher levels on the stack but it will not include any information about the context
       of the error within the procedure.  Typically the info value is supplied from the value left in errorInfo after a catch command trapped	an
       error within the procedure.

       If the -errorcode option is specified then code provides a value for the errorCode variable.  If the option is not specified then errorCode
       will default to NONE.

SEE ALSO

       break(n), continue(n), error(n), proc(n)

KEYWORDS

       break, continue, error, procedure, return

Tcl									7.0								 return(n)
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