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Top Forums UNIX for Dummies Questions & Answers How to print arguments in reverse order? Post 302510220 by royalibrahim on Saturday 2nd of April 2011 03:44:59 AM
Old 04-02-2011
Hi,

I am trying to write a script to sum the series of integers passed as command line arguments to the script.

Code:
#!/bin/bash

while ((n=n+$1)); do
    shift
done
echo $n

the n gives the correct value, ie sum of all the passed positional parameters, but with an error message n=n+: syntax error: operand expected (error token is "+"). I guess, this error message is due to the NULL value after shifting all the positional arguments. Now, my question is, how to make this script work proper? Also, I want to keep this script as compact as it is now.
 

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getopt(1)						      General Commands Manual							 getopt(1)

Name
       getopt - parse command options

Syntax
       set - - getopt optstring $*

Description
       The  command  breaks  up  options in command lines for easy parsing by Shell procedures and checks for legal options.  The optstring option
       letters are recognized if a letter is followed by a colon, the option expects an argument which may or may not  be  separated  from  it	by
       white space.  For further information, see

       The special option, specified by two minus signs (- -), delimits the end of the options.  If the delimiters are used explicitly, recognizes
       it; otherwise, generates it.  In either case, places the delimiter at the end of the options.  The positional parameters ($1 $2 ...) of the
       shell  are reset so that each option is preceded by a single minus sign (-) and is in its own positional parameter; each option argument is
       also parsed into its own positional parameter.

Examples
       The following code fragment shows how you can process the arguments for a command that can take the options a or b, as well as  the  option
       o, which requires an argument:
       #!/bin/sh5
       set -- getopt abo: $*
       if [ $? != 0 ]
       then
	    echo $USAGE
	    exit 2
       fi
       for i in $*
       do
	    case $i in
	    -a | -b)  FLAG=$i; shift;;
	    -o)  OARG=$2; shift 2;;
	    --)  shift; break;;
	    esac
       done
       This code accepts any of the following as equivalent:
       cmd -aoarg file file
       cmd -a -o arg file file
       cmd -oarg -a file file
       cmd -a -oarg -- file file

Diagnostics
       The command prints an error message on the standard error when it encounters an option letter not included in optstring.

See Also
       sh5(1), getopt(3)

																	 getopt(1)
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