Regarding the shift command??? Post: 302112843

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Top Forums Shell Programming and Scripting Regarding the shift command??? Post 302112843 by cfajohnson on Saturday 31st of March 2007 03:39:54 AM

03-31-2007

Registered User

Quote:

Originally Posted by shrao

I am running a program where in I have this command
which is giving error the shift: number is not correct.
can you please tell me how shift actually works?

"The positional parameters from $N+1 ... are renamed to $1 ... If N is not given, it is assumed to be 1.
"

Quote:

the line which is giving error is-
set $PARAM; shift; shift; shift; shift; shift; shift; shift; shift

The is the same as:
Code:
shift 8
Have you checked whether there are as many as 8 parameters?

Quote:

Is it related somewhere to these parameters which is set before this line
PARAM=$*

What ARE you trying to do? What is the point of resetting the already existing parameters? And if you do it that way, you will also be performing word splitting on the parameters.

Quote:

case "$1" in
"-h"|"-H")
give_help
exit -1
;;
"-p"|"-P")
give_params
exit -1
;;
esac

eval REQID=`echo $PARAM | awk ' { split($2, var, "=")
printf("%s", var[2]) }'`
eval LOGIN=`echo $PARAM | awk ' { split($3, var, "=")
printf("%s", var[2]) }'`
eval USRID=`echo $PARAM | awk ' { split($4, var, "=")
printf("%s",var[2]) }'`
eval USRNM=`echo $PARAM | awk ' { split($5, var, "=")
printf("%s", var[2]) }'`
eval PRINT=`echo $PARAM | awk ' { split($6, var, "=")
printf("%s", var[2]) }'`
eval SVOUT=`echo $PARAM | awk ' { split($7, var, "=")
printf("%s", var[2]) }'`
eval COPNO=`echo $PARAM | awk ' { split($8, var, "=")
printf("%s", var[2]) }'`

export PARAM \
REQID \
LOGIN \
USRID \
USRNM \
PRINT \
SVOUT \
COPNO

I'm not going to correct that convoluted code. There are far too many things wrong with it.

Read the man page for your shell, and learn to use getopts.

cfajohnson

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LEARN ABOUT OPENSOLARIS

shift

shift(1)							   User Commands							  shift(1)

NAME

       shift - shell built-in function to traverse either a shell's argument list or a list of field-separated words

SYNOPSIS

   sh
       shift [n]

   csh
       shift [variable]

   ksh
       *shift [n]

   ksh
       +shift [n]

DESCRIPTION

   sh
       The positional parameters from $n+1 ... are renamed $1 ... . If n is not specified, it is assumed to be 1.

   csh
       The  components of argv, or variable, if supplied, are shifted to the left, discarding the first component. It is an error for the variable
       not to be set or to have a null value.

   ksh
       The positional parameters from $n+1 $n+1 ... are renamed $1 ..., default n is 1. The parameter n can  be  any  arithmetic  expression  that
       evaluates to a non-negative number less than or equal to $#.

       On this manual page, ksh(1) commands that are preceded by one or two * (asterisks) are treated specially in the following ways:

	   1.	  Variable assignment lists preceding the command remain in effect when the command completes.

	   2.	  I/O redirections are processed after variable assignments.

	   3.	  Errors cause a script that contains them to abort.

	   4.	  Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a
		  variable assignment. This means that tilde substitution is performed after the = sign and word splitting and file  name  genera-
		  tion are not performed.

   ksh93
       shift  is  a  shell  special  built-in that shifts the positional parameters to the left by the number of places defined by n, or 1 if n is
       omitted. The number of positional parameters remaining is reduced by the number of places that are shifted.

       If n is specified, it is evaluated as an arithmetic expression to determine the number of places to shift. It is an  error  to  shift  more
       than the number of positional parameters or a negative number of places.

       The following exit values are returned by shift in ksh93:

       0     Successful completion. The positional parameters were successfully shifted.

       >0    An error occurred.

       On this manual page, ksh93(1) commands that are preceded by one or two + are treated specially in the following ways:

	   1.	  Variable assignment lists preceding the command remain in effect when the command completes.

	   2.	  I/O redirections are processed after variable assignments.

	   3.	  Errors cause a script that contains them to abort.

	   4.	  They are not valid function names.

	   5.	  Words, following a command preceded by ++ that are in the format of a variable assignment, are expanded with the same rules as a
		  variable assignment. This means that tilde substitution is performed after the = sign and field splitting and file name  genera-
		  tion are not performed.

ATTRIBUTES

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

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

SEE ALSO

       csh(1), ksh(1), ksh93(1), sh(1), attributes(5)

SunOS 5.11							    20 Nov 2007 							  shift(1)

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LEARN ABOUT OPENSOLARIS

shift