Strange function call in the shell script parse_prog_args $@

Shell Programming and Scripting
1

I am converting shell script to Perl. In shell I have a code

 parse_prog_args()
{
  if [ $# -gt 0 ]
  then
    while [ ! -z "$1" ]
    do
      case $1 in
  -P* | -p* )
  export PROCESS_DATE=$2
  export MM=`echo $2 | cut -c5-6`
  export DD=`echo $2 | cut -c7-8`
  export YY=`echo $2 | cut -c3-4`
  export YYYY=`echo $2 | cut -c1-4`
  export PROCESS_DATE_US_MMDDYY="$MM/$DD/$YY"
  shift
  ;;
  -F* | -f* )
  export _REPORT_NAME_=$2
  export _REPORT_NAME_
  shift
  ;;
  -S* | -s* )
  export _SRC_DIR_=$2
  export _SRC_DIR_
  shift
  ;;
  -COPYONLY | -copyonly )
  export _COPY_ONLY_="1"
  export _COPY_ONLY_
  ;;
        *)
        echo "[$1] Argument is invalid"
        echo "Usage:"
        echo "\t$PROG"
        echo "\t\t[-S source_directory]    # provide bps batch job seq. 576 is default"
        echo "\t\t[-F cool_file_name]      # test extraction of price file without sending to ADP"
        echo "\t\t[-P process_date]        # provide bps batch job seq. 576 is default"
        echo "\t\t[-COPYONLY]              # provide bps batch job seq. 576 is default"
        exit
        ;;
      esac
      shift
    done
  fi
}
 parse_prog_args $@

What I don't understand is, why shell require such function call

 parse_prog_args $@

What it sends to the function?

Thanks for contribution

1 Like
2

man ksh yields:

   Special Parameters
       The shell treats several parameters specially.  These parameters may only be referenced; assignment to  them  is
       not allowed.
       *      Expands to the positional parameters, starting from one.  When the expansion is not within double quotes,
              each positional parameter expands to a separate word.  In contexts where it is performed, those words are
              subject  to  further  word  splitting  and  pathname  expansion.  When the expansion occurs within double
              quotes, it expands to a single word with the value of each parameter separated by the first character  of
              the  IFS special variable.  That is, "$*" is equivalent to "$1c$2c...", where c is the first character of
              the value of the IFS variable.  If IFS is unset, the parameters are separated by spaces.  If IFS is null,
              the parameters are joined without intervening separators.
       @      Expands to the positional parameters, starting from one.  When the expansion occurs within double quotes,
              each parameter expands to a separate word.  That is, "$@" is equivalent to "$1" "$2" ...  If the  double-
              quoted  expansion occurs within a word, the expansion of the first parameter is joined with the beginning
              part of the original word, and the expansion of the last parameter is joined with the last  part  of  the
              original  word.   When  there are no positional parameters, "$@" and $@ expand to nothing (i.e., they are
              removed).
3

Fromm your explanation we don't need this function, or we need to send clearly parameters. Please I don't have bash. it is an old system AIX and we use

 #!/bin/sh

Thanks for contribution

4

Hmm....
your parse_prog_args functions takes the arguments [$@] from the list past to the script at the point of a call. I don't see how you can state that we don't need this function, or we need to send clearly parameters or what it means...
Your /bin/sh interpreter most likely has the same functionality for $@ as bash - man sh for details.

5

Now I understand. Everything what is left, to figure out, how to make it works in Perl

Thanks for contribution