#!/bin/bash
## receives two filenames; returns TRUE iff 1st is leading-subset-of-or-equal-to 2nd;  Eugene Reimer  2010-03;
## was a function in WEBGETLOGS, but may be useful elsewhere;

CMPMSG=$(cmp $1 $2 2>&1)						##compare using cmp
if [[ $CMPMSG == "" || $CMPMSG == "cmp: EOF on $1" ]];then exit 0; fi	##they're identical OR $1 is leading subset of $2, so indicate TRUE
exit 99									##otherwise indicate FALSE


NOTES:
======
now using cmp on entire files w/o "-s" then checking its output for:  emptystring (indicates EQUAL)  or cmp's subset-msg which looks like:  cmp: EOF on FILENAME,  
	where we need to ensure that FILENAME names the $1 file;
	BEWARE: one kind of cmp-msg goes to stdout, the other goes to stderr==!!==

my first thought (for the use in WEBGETLOGS) was to compare only first lines AND file-sizes, then realized a simpler test would also do a better job;
Obsolete first version:
	sz1=$(ls -l $1 |arr 5);  head -n1 $1 >/tmp/SubsetOrEqual-1				##get filesize and isolate first line
	sz2=$(ls -l $2 |arr 5);  head -n1 $2 >/tmp/SubsetOrEqual-2
	if cmp -s /tmp/SubsetOrEqual-1 /tmp/SubsetOrEqual-2 && ((sz2>=sz1));then  exit 0; fi	##first records match and $2 as big, so indicate TRUE
	exit 99											##otherwise indicate FALSE