A $(( expression )) bug? Post: 302982348

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Top Forums UNIX for Advanced & Expert Users A $(( expression )) bug? Post 302982348 by wisecracker on Wednesday 28th of September 2016 09:07:20 AM

09-28-2016

Registered User

Quote:

Originally Posted by Don Cragun

In an arithmetic evaluation, the value of a variable can be specified by expanding the variable (i.e. $var or ${var}) or by just giving the variable name (i.e. var). But the expression that is the numeric evaluation of the length of the string that is the value of a variable must use the expansion of the variable that produces that number (i.e. ${#var}); you cannot skip the ${ and } when you are using shell variable expansion operators like ${#var} or ${var%%pattern} or ${var:offset:length}.

OK, I'll go with that BUT, and a big but, why does Shell Check echo "$(( #txt - 1 ))" NOT come up with a syntax error knowing from the various scenarios that it does?
Should there not be a warning saying so. Note that in the Shell Check example I was using the worst case sh . Tested on the others gave errors or incorrect results too.
On reading RudiC's post it looks as though it SHOULD work but obviously it doesn't, or I am misinterpreting it?
Anyhow thanks, but I will keep '$/${}' in all cases just to be on the safe side.

wisecracker

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colorreset

COLORS(3)						   libbash colors Library Manual						 COLORS(3)

NAME

     colors -- libbash library for setting tty colors.

SYNOPSIS

     colorSet	  <color>
     colorReset
     colorPrint   [<indent>] <color> <text>
     colorPrintN  [<indent>] <color> <text>

DESCRIPTION

   General
     colors is a collection of functions that make it very easy to put colored text on tty.

     The function list:
	   colorSet	    Sets the color of the prints to the tty to COLOR
	   colorReset	    Resets current tty color back to normal
	   colorPrint	    Prints TEXT in the color COLOR indented by INDENT (without adding a newline)
	   colorPrintN	    The same as colorPrint, but trailing newline is added

     Detailed interface description follows.

   Available colors:
	   Green
	   Red
	   Yellow
	   White
     The color parameter is non-case-sensitive (i.e. RED, red, ReD, and all the other forms are valid and are the same as Red).

FUNCTIONS DESCRIPTIONS

   colorSet <color>
     Sets the current printing color to color.

   colorReset
     Resets current tty color back to normal.

   colorPrint [<indent>] <color>
     Prints text using the color color indented by indent (without adding a newline).

     Parameters:

       <indent>
	 The column to move to before start printing.  This parameter is optional. If ommitted - start output from current cursor position.

       <color>
	 The color to use.

       <color>
	 The text to print.

   colorPrintN [<indent>] <color>
     The same as colorPrint, except a trailing newline is added.

EXAMPLES

     Printing a green 'Hello World' with a newline:

	  Using colorSet:
		  $ colorSet green
		  $ echo 'Hello World'
		  $ colorReset

	  Using colorPrint:
		  $ colorPrint 'Hello World'; echo

	  Using colorPrintN:
		  $ colorPrintN 'Hello World'

AUTHORS

     Hai Zaar <haizaar@haizaar.com>
     Gil Ran <gil@ran4.net>

SEE ALSO

     ldbash(1), libbash(1)

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