FGETTR - Routines to get an SU trace from a file 

fgettr		get a fixed-length segy trace from a file by file pointer
fvgettr		get a variable-length segy trace from a file by file pointer
fgettra		get a fixed-length trace from disk file by trace number
gettr		macro using fgettr to get a trace from stdin
vgettr		macro using vfgettr to get a trace from stdin
gettra		macro using fgettra to get a trace from stdin by trace number
 
Function Prototype:
int fgettr(FILE *fp, segy *tp);
int fvgettr(FILE *fp, segy *tp);
int fgettra(FILE *fp, segy *tp, int itr);

Returns:
fgettr, fvgettr:
int: number of bytes read on current trace (0 after last trace)

fgettra:
int: number of traces in disk file
 
Macros defined in segy.h
define gettr(x)	fgettr(stdin, (x))
define vgettr(x)	fgettr(stdin, (x))

Usage example:
 	segy tr;
 	...
 	while (gettr(&tr)) {
 		tr.offset = abs(tr.offset);
 		puttr(&tr);
 	}
 	...

Authors: SEP: Einar Kjartansson, Stew Levin CWP: Shuki Ronen, Jack Cohen

 Revised: 7/2/95 Stewart A. Levin   Mobil
     Major rewrite:  Use xdr library for portable su output file
     format.   Merge fgettr and fgettra into same source file.
     Make input from multiple streams work (at long last!).
 Revised: 11/22/95 Stewart A. Levin  Mobil
     Always set ntr for DISK input.  This fixes susort failure.
 Revised: 1/9/96  jkc CWP
     Set lastfp on nread <=0 return, too.