Help with bash shell scripting Post: 302513220

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Homework and Emergencies Homework & Coursework Questions Help with bash shell scripting Post 302513220 by Corona688 on Tuesday 12th of April 2011 02:59:36 PM

04-12-2011

Registered User

Quote:

Originally Posted by DGPickett

But then it might not be ksh portable![CODE]$ echo "(( 1 + 2 ))"
(( 1 + 2 ))
$ echo (( 1 + 2 ))
ksh: syntax error: `((' unexpected

That's not "unportable" -- that's simply wrong. BASH and KSH alike agree this is a syntax error, and for good reason:

Produces a string: $((stuff))
Produces no string: ((stuff))

Plain (( )) without the $ is more like a [ ] statement. Try it:

Code:

if ((0)) ; then echo asdf ; fi
if ((1)) ; then echo asdf ; fi

When you use them in a syntactically valid manner, as their own statement, they're fine: ((k = k + 5))

You also missed my point about k vs $k inside (( )). ((k=k+3)) works, (($k=$k+3)) does not since K gets substituted before anything starts calculating, so you end up trying to assign the value of 3 or something. Just plain variable names don't ever need a $ inside a (( )) expression anyway, why make them more complicated?

Last edited by Corona688; 04-12-2011 at 04:08 PM..

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LEARN ABOUT SUNOS

print

print(1)							   User Commands							  print(1)

NAME

       print - shell built-in function to output characters to the screen or window

SYNOPSIS

   ksh
       print [ -Rnprsu [n]] [arg...]

DESCRIPTION

   ksh
       The shell output mechanism. With no flags or with flag - or -, the arguments are printed on standard output as described by echo(1).

OPTIONS

       The following options are supported:

       -n	       suppresses new-line from being added to the output.

       -R

       -r	       (raw  mode) ignore the escape conventions of echo. The -R option will print all subsequent arguments and options other than
		       -n.

       -p	       causes the arguments to be written onto the pipe of the process spawned with |& instead of standard output.

       -s	       causes the arguments to be written onto the history file instead of standard output.

       -u [ n ]        flag can be used to specify a one digit file descriptor unit number n on which the output will be placed. The default is 1.

EXIT STATUS

       The following exit values are returned:

       0	Successful operation.

       >0	Output file is not open for writing.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       echo(1), ksh(1), attributes(5)

SunOS 5.10							    15 Apr 1994 							  print(1)

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