Binary Grep and Binary Pattern Replace

bgrep.c

#include <stdio.h>
#include <string.h>

void usage(char* progname) {
	fprintf(stderr, "%s pattern [files]\n", progname);
}

void search(char* pattern, FILE* in, char* prefix) {
	int c;
	unsigned long long offset = 0;
	unsigned long long foundOffset = offset;
	char* start = pattern;

	if (!in) in = stdin;
	c = fgetc(in);
	while (c != EOF) {
		if (c == *start) {
			if (start == pattern) foundOffset = offset;
			++start;
		}
		else {
			start = pattern;
		}
		if (!*start) {
			if (prefix && *prefix) printf("%s:", prefix);
			printf("%llu\n", foundOffset);
			start = pattern;
		}
		++offset;
		c = fgetc(in);
	}
}

int main(int argc, char* argv[]) {
	char* pattern;
	int i;
	if (argc < 2) {
		usage(argv[0]);
		return -1;
	}
	pattern = argv[1];
	for (i = 2; i < argc; ++i) {
		FILE* in = NULL;
		char* prefix = NULL;
		if (strcmp(argv[i], "-") != 0) {
			prefix = argv[i];
			in = fopen(argv[i], "rb");
			if (!in) {
				fprintf(stderr, "Unable to open: %s\n", argv[i]);
				return -1;
			}
		}
		search(pattern, in, prefix);
		if (in) fclose(in);
	}
	return 0;
}

breplace.c

#include <stdio.h>
#include <string.h>

void usage(char* progname) {
	fprintf(stderr, "%s pattern modPattern [file] [fileOut]\n", progname);
	fprintf(stderr,
		"\tNOTE: modPattern and pattern must be of the same length\n");
}

void searchAndReplace(char* pattern, char* modPattern, FILE* in, FILE* out) {
	int c;
	unsigned long long offset = 0;
	unsigned long long foundOffset = offset;
	char* start = pattern;

	if (!in) in = stdin;
	if (!out) out = stdout;
	c = fgetc(in);
	while (c != EOF) {
		if (c == *start) {
			if (start == pattern) foundOffset = offset;
			++start;
		}
		else {
			if (start != pattern) {
				fwrite(pattern, offset - foundOffset, sizeof(char), out);
			}
			fputc(c, out);
			start = pattern;
		}
		if (!*start) {
			fwrite(modPattern, offset - foundOffset + 1, sizeof(char), out);
			start = pattern;
		}
		++offset;
		c = fgetc(in);
	}
}

int main(int argc, char* argv[]) {
	char* pattern;
	char* modPattern;
	FILE* in = NULL;
	FILE* out = NULL;
	if (argc < 3) {
		usage(argv[0]);
		return -1;
	}
	pattern = argv[1];
	modPattern = argv[2];
	if (strlen(pattern) != strlen(modPattern)) {
		usage(argv[0]);
		return -1;
	}
	if (argc > 3 && strcmp(argv[3], "-") != 0) {
		in = fopen(argv[3], "rb");
		if (!in) {
			fprintf(stderr, "Unable to open: %s\n", argv[3]);
			return -1;
		}
	}
	if (argc > 4 && strcmp(argv[4], "-") != 0) {
		out = fopen(argv[4], "wb");
		if (!out) {
			fprintf(stderr, "Unable to open: %s\n", argv[4]);
			return -1;
		}
	}
	searchAndReplace(pattern, modPattern, in, out);
	return 0;
}