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Full Discussion: Variables and math in Old skool Bourne Shell
Top Forums UNIX for Dummies Questions & Answers Variables and math in Old skool Bourne Shell Post 302677229 by mr.rhtuner on Wednesday 25th of July 2012 06:53:46 PM
Old 07-25-2012
Variables and math in Old skool Bourne Shell
Hey everybody, I've been searching google and these forums and have found some solutions to the issues I've been having today within the OLD Bourne Shell. I am following chapter 6 of the Guide to Unix using Linux 4th Edition.

I am working on some basic calculations with variables in the BASH SHELL and doing the same within the Bourne Shell with modifications.

In BASH, I did the following:

Code:
let X=10+2*7
Type echo $X and press Enter. You see 24 on the screen.

Now I realize that the bourne shell does NOT have LET as a command, and I need to use expr.

I was able to get the math to work, by doing the following:

Code:
$ expr 10 + 2 '*' 7
24 is the answer.

But how do I incorporate the variable of X into this?

I tried:

Code:
$ X=%((10 + 2 '*' 7))
but get the error: synatx error: 'X=% unexpected


Anybody mind giving me an idea what I am doing wrong?
 

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LEARN ABOUT DEBIAN

sdl::gfx::imagefilter

pods::SDL::GFX::ImageFilter(3pm)			User Contributed Perl Documentation			  pods::SDL::GFX::ImageFilter(3pm)

NAME

       SDL::GFX::ImageFilter - image filtering functions

CATEGORY

       TODO, GFX

METHODS

   MMX_detect
       int gfx_image_MMX_detect()      CODE:	       SDL_imageFilterMMXdetect();

   MMX_off
       void gfx_image_MMX_off()      CODE:	     SDL_imageFilterMMXoff();

   MMX_on
       void gfx_image_MMX_on()	    CODE:	    SDL_imageFilterMMXon();

   add
       int gfx_image_add(Src1, Src2, Dest, length)	unsigned char *Src1	 unsigned char *Src2	  unsigned char *Dest	   int length
	    CODE:	    RETVAL = SDL_imageFilterAdd(Src1, Src2, Dest, length);	OUTPUT: 	  RETVAL

   mean
       int gfx_image_mean(Src1, Src2, Dest, length)	 unsigned char *Src1	  unsigned char *Src2	   unsigned char *Dest	    int length
	    CODE:	    RETVAL = SDL_imageFilterMean(Src1, Src2, Dest, length);	 OUTPUT:	   RETVAL

   sub
       int gfx_image_sub(Src1, Src2, Dest, length)	unsigned char *Src1	 unsigned char *Src2	  unsigned char *Dest	   int length
	    CODE:	    RETVAL = SDL_imageFilterSub(Src1, Src2, Dest, length);	OUTPUT: 	  RETVAL

   abs_diff
       int gfx_image_abs_diff(Src1, Src2, Dest, length)      unsigned char *Src1      unsigned char *Src2      unsigned char *Dest	int length
	    CODE:	    RETVAL = SDL_imageFilterAbsDiff(Src1, Src2, Dest, length);	    OUTPUT:	      RETVAL

   mult
       int gfx_image_mult(Src1, Src2, Dest, length)	 unsigned char *Src1	  unsigned char *Src2	   unsigned char *Dest	    int length
	    CODE:	    RETVAL = SDL_imageFilterMult(Src1, Src2, Dest, length);	 OUTPUT:	   RETVAL

   mult_nor
       int gfx_image_mult_nor(Src1, Src2, Dest, length)      unsigned char *Src1      unsigned char *Src2      unsigned char *Dest	int length
	    CODE:	    RETVAL = SDL_imageFilterMultNor(Src1, Src2, Dest, length);	    OUTPUT:	      RETVAL

   mult_div_by_2
       int gfx_image_mult_div_by_2(Src1, Src2, Dest, length)	  unsigned char *Src1	   unsigned char *Src2	    unsigned char *Dest      int
       length	   CODE:	   RETVAL = SDL_imageFilterMultDivby2(Src1, Src2, Dest, length);      OUTPUT:		RETVAL

   mult_div_by_4
       int gfx_image_mult_div_by_4(Src1, Src2, Dest, length)	  unsigned char *Src1	   unsigned char *Src2	    unsigned char *Dest      int
       length	   CODE:	   RETVAL = SDL_imageFilterMultDivby4(Src1, Src2, Dest, length);      OUTPUT:		RETVAL

   bit_and
       int gfx_image_bit_and(Src1, Src2, Dest, length)	    unsigned char *Src1      unsigned char *Src2      unsigned char *Dest      int length
	    CODE:	    RETVAL = SDL_imageFilterBitAnd(Src1, Src2, Dest, length);	   OUTPUT:	     RETVAL

   bit_or
       int gfx_image_bit_or(Src1, Src2, Dest, length)	   unsigned char *Src1	    unsigned char *Src2      unsigned char *Dest      int length
	    CODE:	    RETVAL = SDL_imageFilterBitOr(Src1, Src2, Dest, length);	  OUTPUT:	    RETVAL

   div
       int gfx_image_div(Src1, Src2, Dest, length)	unsigned char *Src1	 unsigned char *Src2	  unsigned char *Dest	   int length
	    CODE:	    RETVAL = SDL_imageFilterDiv(Src1, Src2, Dest, length);	OUTPUT: 	  RETVAL

   bit_negation
       int gfx_image_bit_negation(Src1, Dest, length)	   unsigned char *Src1	    unsigned char *Dest      int length      CODE:
		 RETVAL = SDL_imageFilterBitNegation(Src1, Dest, length);      OUTPUT:		 RETVAL

   add_byte
       int gfx_image_add_byte(Src1, Dest, length, C)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned char C
	    CODE:	    RETVAL = SDL_imageFilterAddByte(Src1, Dest, length, C);	 OUTPUT:	   RETVAL

   add_uint
       int gfx_image_add_uint(Src1, Dest, length, C)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned int C
	    CODE:	    RETVAL = SDL_imageFilterAddUint(Src1, Dest, length, C);	 OUTPUT:	   RETVAL

   add_byte_to_half
       int gfx_image_add_byte_to_half(Src1, Dest, length, C)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned char
       C      CODE:	      RETVAL = SDL_imageFilterAddByteToHalf(Src1, Dest, length, C);	 OUTPUT:	   RETVAL

   sub_byte
       int gfx_image_sub_byte(Src1, Dest, length, C)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned char C
	    CODE:	    RETVAL = SDL_imageFilterSubByte(Src1, Dest, length, C);	 OUTPUT:	   RETVAL

   sub_uint
       int gfx_image_sub_uint(Src1, Dest, length, C)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned int C
	    CODE:	    RETVAL = SDL_imageFilterSubUint(Src1, Dest, length, C);	 OUTPUT:	   RETVAL

   shift_right
       int gfx_image_shift_right(Src1, Dest, length, N)      unsigned char *Src1      unsigned char *Dest      int length      unsigned char N
	    CODE:	    RETVAL = SDL_imageFilterShiftRight(Src1, Dest, length, N);	    OUTPUT:	      RETVAL

   shift_right_uint
       int gfx_image_shift_right_uint(Src1, Dest, length, N)	  unsigned char *Src1	   unsigned char *Dest	    int length	    unsigned char
       N      CODE:	      RETVAL = SDL_imageFilterShiftRightUint(Src1, Dest, length, N);	  OUTPUT:	    RETVAL

   mult_by_byte
       int gfx_image_mult_by_byte(Src1, Dest, length, C)      unsigned char *Src1      unsigned char *Dest	int length	unsigned char C
	    CODE:	    RETVAL = SDL_imageFilterMultByByte(Src1, Dest, length, C);	    OUTPUT:	      RETVAL

   shift_right_and_mult_by_byte
       int gfx_image_shift_right_and_mult_by_byte(Src1, Dest, length, N, C)	 unsigned char *Src1	  unsigned char *Dest	   int length
	    unsigned char N	 unsigned char C      CODE:	      RETVAL = SDL_imageFilterShiftRightAndMultByByte(Src1, Dest, length, N, C);
	    OUTPUT:	      RETVAL

   shift_left_byte
       int gfx_image_shift_left_byte(Src1, Dest, length, N)	 unsigned char *Src1	  unsigned char *Dest	   int length	   unsigned char N
	    CODE:	    RETVAL = SDL_imageFilterShiftLeftByte(Src1, Dest, length, N);      OUTPUT:		 RETVAL

   shift_left_uint
       int gfx_image_shift_left_uint(Src1, Dest, length, N)	 unsigned char *Src1	  unsigned char *Dest	   int length	   unsigned char N
	    CODE:	    RETVAL = SDL_imageFilterShiftLeftUint(Src1, Dest, length, N);      OUTPUT:		 RETVAL

   shift_left
       int gfx_image_shift_left(Src1, Dest, length, N)	    unsigned char *Src1      unsigned char *Dest      int length      unsigned char N
	    CODE:	    RETVAL = SDL_imageFilterShiftLeft(Src1, Dest, length, N);	   OUTPUT:	     RETVAL

   binarize_using_threshold
       int gfx_image_binarize_using_threshold(Src1, Dest, length, T)	  unsigned char *Src1	   unsigned char *Dest	    int length
	    unsigned char T	 CODE:		 RETVAL = SDL_imageFilterBinarizeUsingThreshold(Src1, Dest, length, T);      OUTPUT:
		 RETVAL

   clip_to_range
       int gfx_image_clip_to_range(Src1, Dest, length, Tmin, Tmax)	unsigned char *Src1	 unsigned char *Dest	  int length	  unsigned
       char Tmin      unsigned char Tmax      CODE:	      RETVAL = SDL_imageFilterClipToRange(Src1, Dest, length, Tmin, Tmax);	OUTPUT:
		 RETVAL

   normalize_linear
       int gfx_image_normalize_linear(Src1, Dest, length, Cmin, Cmax, Nmin, Nmax)      unsigned char *Src1	unsigned char *Dest	 int
       length	   int Cmin	 int Cmax      int Nmin      int Nmax	   CODE:	   RETVAL = SDL_imageFilterNormalizeLinear(Src1, Dest,
       length, Cmin, Cmax, Nmin, Nmax);      OUTPUT:	       RETVAL

   convolve_kernel_3x3_divide
       int gfx_image_convolve_kernel_3x3_divide(Src, Dest, rows, columns, Kernel, Divisor)	unsigned char *Src	unsigned char *Dest
	    int rows	  int columns	   Sint16 *Kernel      unsigned char Divisor	  CODE: 	  RETVAL =
       SDL_imageFilterConvolveKernel3x3Divide(Src, Dest, rows, columns, Kernel, Divisor);      OUTPUT:		 RETVAL

   convolve_kernel_5x5_divide
       int gfx_image_convolve_kernel_5x5_divide(Src, Dest, rows, columns, Kernel, Divisor)	unsigned char *Src	unsigned char *Dest
	    int rows	  int columns	   Sint16 *Kernel      unsigned char Divisor	  CODE: 	  RETVAL =
       SDL_imageFilterConvolveKernel5x5Divide(Src, Dest, rows, columns, Kernel, Divisor);      OUTPUT:		 RETVAL

   convolve_kernel_7x7_divide
       int gfx_image_convolve_kernel_7x7_divide(Src, Dest, rows, columns, Kernel, Divisor)	unsigned char *Src	unsigned char *Dest
	    int rows	  int columns	   Sint16 *Kernel      unsigned char Divisor	  CODE: 	  RETVAL =
       SDL_imageFilterConvolveKernel7x7Divide(Src, Dest, rows, columns, Kernel, Divisor);      OUTPUT:		 RETVAL

   convolve_kernel_9x9_divide
       int gfx_image_convolve_kernel_9x9_divide(Src, Dest, rows, columns, Kernel, Divisor)	unsigned char *Src	unsigned char *Dest
	    int rows	  int columns	   Sint16 *Kernel      unsigned char Divisor	  CODE: 	  RETVAL =
       SDL_imageFilterConvolveKernel9x9Divide(Src, Dest, rows, columns, Kernel, Divisor);      OUTPUT:		 RETVAL

   convolve_kernel_3x3_shift_right
       int gfx_image_convolve_kernel_3x3_shift_right(Src, Dest, rows, columns, Kernel, NRightShift)	 unsigned char *Src	 unsigned char
       *Dest	  int rows	int columns	 Sint16 *Kernel      unsigned char NRightShift	    CODE:	    RETVAL =
       SDL_imageFilterConvolveKernel3x3ShiftRight(Src, Dest, rows, columns, Kernel, NRightShift);      OUTPUT:		 RETVAL

   convolve_kernel_5x5_shift_right
       int gfx_image_convolve_kernel_5x5_shift_right(Src, Dest, rows, columns, Kernel, NRightShift)	 unsigned char *Src	 unsigned char
       *Dest	  int rows	int columns	 Sint16 *Kernel      unsigned char NRightShift	    CODE:	    RETVAL =
       SDL_imageFilterConvolveKernel5x5ShiftRight(Src, Dest, rows, columns, Kernel, NRightShift);      OUTPUT:		 RETVAL

   convolve_kernel_7x7_shift_right
       int gfx_image_convolve_kernel_7x7_shift_right(Src, Dest, rows, columns, Kernel, NRightShift)	 unsigned char *Src	 unsigned char
       *Dest	  int rows	int columns	 Sint16 *Kernel      unsigned char NRightShift	    CODE:	    RETVAL =
       SDL_imageFilterConvolveKernel7x7ShiftRight(Src, Dest, rows, columns, Kernel, NRightShift);      OUTPUT:		 RETVAL

   convolve_kernel_9x9_shift_right
       int gfx_image_convolve_kernel_9x9_shift_right(Src, Dest, rows, columns, Kernel, NRightShift)	 unsigned char *Src	 unsigned char
       *Dest	  int rows	int columns	 Sint16 *Kernel      unsigned char NRightShift	    CODE:	    RETVAL =
       SDL_imageFilterConvolveKernel9x9ShiftRight(Src, Dest, rows, columns, Kernel, NRightShift);      OUTPUT:		 RETVAL

   sobel_x
       int gfx_image_sobel_x(Src, Dest, rows, columns)	    unsigned char *Src	    unsigned char *Dest      int rows	   int columns	    CODE:
		 RETVAL = SDL_imageFilterSobelX(Src, Dest, rows, columns);	OUTPUT: 	  RETVAL

   sobel_x_shift_right
       int gfx_image_sobel_x_shift_right(Src, Dest, rows, columns, NRightShift)      unsigned char *Src      unsigned char *Dest      int rows
	    int columns      unsigned char NRightShift	    CODE:	    RETVAL = SDL_imageFilterSobelXShiftRight(Src, Dest, rows, columns,
       NRightShift);	  OUTPUT:	    RETVAL

   align_stack
       void gfx_image_align_stack()	 CODE:		 SDL_imageFilterAlignStack();

   restore_stack
       void gfx_image_restore_stack()	   CODE:	   SDL_imageFilterRestoreStack();

AUTHORS

       See "AUTHORS" in SDL.

perl v5.14.2							    2012-05-28					  pods::SDL::GFX::ImageFilter(3pm)
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