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Full Discussion: setting variable value to dynamic sed match - escaping hell
Top Forums Shell Programming and Scripting setting variable value to dynamic sed match - escaping hell Post 302468899 by aedgar on Thursday 4th of November 2010 05:57:25 AM
Old 11-04-2010
Question setting variable value to dynamic sed match - escaping hell
Hello All,

I'm trying to write a script that will perform a dynamic match (of a dynamic variable) and set a variable to have the resulting (match) value.

The idea is that the environment variable to check ($1) and the regular expression to use ($2) are given as parameters.

For example, to print the user's username only if it begins with an 'a', we would make the call:
Code:
check-var.sh USER "^a.*$"

I've tried doing this:
Code:
VAR_NAME=$1
 
VAR_REGEXP=$2
 
VAR_MATCH=`eval "echo \$${VAR_NAME} | sed -n \"/$VAR_REGEXP/p\""
 
echo $VAR_MATCH

But there seems to be a problem with by quoting and escaping because if I execute the eval directly like this:
Code:
eval "echo \$${VAR_NAME} | sed -n \"/$VAR_REGEXP/p\""

the expected result is printed.

Anyone out there have an idea of how I can capture the result in the VAR_MATCH variable? I ask because I actually need to work with the matched value later on in the script and not simply send it to stdout.

Thanks,
- Andy
Last edited by Scott; 11-04-2010 at 07:20 AM.. Reason: Please use code tags
 

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LEARN ABOUT DEBIAN

extract_font_range

extract_font_range(3alleg4)					  Allegro manual				       extract_font_range(3alleg4)

NAME

       extract_font_range - Extracts a range of characters from a font. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       FONT *extract_font_range(FONT *f, int begin, int end)

DESCRIPTION

       This  function  extracts  a  character range from a font and returns a new font that contains only the range of characters selected by this
       function. You can pass -1 for either the lower or upper bound if you want to select all characters from the start or  to  the  end  of  the
       font.  Example:

	  FONT *myfont;
	  FONT *capitals;
	  FONT *fontcopy;
	  ...
	  /* Create a font of only capital letters */
	  capitals = extract_font_range(myfont, 'A', 'Z');

	  /* Create a copy of the font */
	  fontcopy = extract_font_range(myfont, -1, -1);
	  ...
	  destroy_font(capitals);
	  destroy_font(fontcopy);

RETURN VALUE

       Returns a pointer to the new font or NULL on error. Remember that you are responsible for destroying the font when you are finished with it
       to avoid memory leaks.

SEE ALSO

       get_font_range_begin(3alleg4), get_font_range_end(3alleg4), merge_fonts(3alleg4), transpose_font(3alleg4), exfont(3alleg4)

Allegro 							   version 4.4.2				       extract_font_range(3alleg4)
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