/* file: pbs-not.c		G. Moody		29 February 2012

Read a list of records, write a list of missing records (logical "not")

This program must receive two arguments (filenames of a list of all records,
and of the list of records to be complemented).
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define LMAX 128

char **line;
FILE **ifile;
int n;

/* cleanup: close input files, free allocated memory, and quit. */
void cleanup()
{
    if (ifile && ifile[0]) {	/* copy remaining missing files to stdout */
	while (fgets(line[0], LMAX, ifile[0]))
	    fputs(line[0], stdout);
    }
    while (n-- > 0) {
	fclose(ifile[n]);
	if (line[n]) free(line[n]);
    }
    if (line) free(line);
    if (ifile) free(ifile);
    exit(0);
}

/* init: open input files and read the first line of each. */
void init(int argc, char **argv)
{
    if (argc != 3)	/* exactly two inputs required */
	exit(1);

    argc--; argv++;	/* skip argv[0] */
    ifile = (FILE **)calloc(argc, sizeof(FILE *));
    line = (char **)calloc(argc, sizeof(char *));
    for (n = 0; n < 2; n++) {
	if ((ifile[n] = fopen(argv[n], "r")) == NULL)
	    cleanup();
	line[n] = (char *)calloc(LMAX, sizeof(char));
    }
    if (fgets(line[1], LMAX, ifile[1]) == NULL)
	    cleanup();
}

main(int argc, char **argv)
{
    init(argc, argv);

    while (1) {
	int i;

	if ((i = strcmp(line[0], line[1])) < 0) {
	    fputs(line[0], stdout);
	    if (fgets(line[0], LMAX, ifile[0]) == NULL)
		cleanup();
	}
	else if (i == 0) {
	    if (fgets(line[1], LMAX, ifile[1]) == NULL ||
		fgets(line[0], LMAX, ifile[0]) == NULL)
		cleanup();
	}
	else { /* this shouldn't happen! */
	    if (fgets(line[1], LMAX, ifile[1]) == NULL)
		cleanup();
	}
    };

    cleanup();
}