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Full Discussion: awk question : system output to awk variable.
Top Forums Shell Programming and Scripting awk question : system output to awk variable. Post 302797491 by Yoda on Monday 22nd of April 2013 04:17:06 PM
Old 04-22-2013
An excerpt from awk manual
Code:
expression | getline [var]

Read a record of input from a stream piped from the output of a command. The stream will be created if no stream is currently open with the value 
of expression as its command name. The stream created will be equivalent to one created by a call to the popen() function with the value of expression 
as the command argument and a value of r as the mode argument. As long as the stream remains open, subsequent calls in which expression evaluates 
to the same string value will read subsequent records from the file. The stream will remain open until the close function is called with an expression 
that evaluates to the same string value. At that time, the stream will be closed as if by a call to the pclose() function. If var is missing, $0 and 
NF will be set; otherwise, var will be set. The getline operator can form ambiguous constructs when there are 
unparenthesised operators (including concatenate) to the left of the "|" (to the beginning of the expression containing getline). 
In the context of the "$" operator, "|" behaves as if it had a lower precedence than "$". The result of evaluating other operators is 
unspecified, and portable applications must parenthesis properly all such usages.

 

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LEARN ABOUT FREEBSD

dwarf_new_expr

DWARF_NEW_EXPR(3)					   BSD Library Functions Manual 					 DWARF_NEW_EXPR(3)

NAME

     dwarf_new_expr -- create a location expression descriptor

LIBRARY

     DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

     #include <libdwarf.h>

     Dwarf_P_Expr
     dwarf_new_expr(Dwarf_P_Debug dbg, Dwarf_Error *err);

DESCRIPTION

     Function dwarf_new_expr() allocates a DWARF location expression descriptor used to build up a location expression stream.

     The application can use the functions dwarf_add_expr_gen(3) and dwarf_add_expr_addr_b(3) to add location expression operators to the created
     descriptor.  When done, the application can call the function dwarf_expr_into_block(3) to retrieve the generated byte stream for the location
     expression, or call the function dwarf_add_AT_location_expr(3) to create an attribute with the location expression stream as its value.

     Argument dbg should reference a DWARF producer instance allocated using dwarf_producer_init(3) or dwarf_producer_init_b(3).

     If argument err is not NULL, it will be used to store error information in case of an error.

RETURN VALUES

     On success, function dwarf_new_expr() returns the created location expression descriptor.	In case of an error, function dwarf_new_expr()
     returns DW_DLV_BADADDR and sets the argument err.

ERRORS

     Function dwarf_new_expr() can fail with:

     [DW_DLE_ARGUMENT]	Argument dbg was NULL.

     [DW_DLE_MEMORY]	An out of memory condition was encountered during the execution of the function.

EXAMPLES

     To create a location expression descriptor, add location expression operators to it and to retrieve the generated byte stream, use:

	   Dwarf_P_Debug dbg;
	   Dwarf_Error de;
	   Dwarf_P_Expr pe;
	   Dwarf_Addr buf;
	   Dwarf_Unsigned len;

	   /* ...Assume that `dbg' refers to a DWARF producer instance... */

	   if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) {
		   warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1));
		   return;
	   }

	   if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) ==
	       DW_DLV_NOCOUNT) {
		   warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1));
		   return;
	   }

	   if ((buf = dwarf_expr_into_block(pe, &len, &de)) ==
	       DW_DLV_BADADDR) {
		   warnx("dwarf_expr_into_block failed: %s",
		       dwarf_errmsg(-1));
		   return;
	   }

SEE ALSO

     dwarf(3), dwarf_add_AT_location_expr(3), dwarf_add_expr_gen(3), dwarf_add_expr_addr(3), dwarf_add_expr_addr_b(3),
     dwarf_expr_current_offset(3), dwarf_expr_into_block(3), dwarf_producer_init(3), dwarf_producer_init_b(3)

BSD
								 September 8, 2011							       BSD
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