utils-std

cmp.c (3484B)

// utils-std: Collection of commonly available Unix tools
// SPDX-FileCopyrightText: 2017 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: MPL-2.0
#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>  // fopen, fprintf, getline
#include <stdlib.h> // abort, strtoul
#include <string.h> // strerror
#include <unistd.h> // getopt
static bool opt_s = false, opt_l = false;
static unsigned long max_bytes = 0;
#undef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
static int
do_cmp(FILE *file1, const char *name1, FILE *file2, const char *name2)
{
	char *line1 = NULL, *line2 = NULL;
	size_t len1 = 0, len2 = 0;
	unsigned long pos = 1, ln = 1;
	while(true)
	{
		ssize_t nread1 = getline(&line1, &len1, file1);
		if(nread1 < 0)
		{
			if(!ferror(file1)) return 0;
			fprintf(
			    stderr, "cmp: Failed to read line %ld from file '%s': %s\n", ln, name1, strerror(errno));
			return 1;
		}
		ssize_t nread2 = getline(&line2, &len2, file2);
		if(nread2 < 0)
		{
			if(!ferror(file2))
			{
				if(!opt_s) fprintf(stderr, "cmp: EOF on %s line %ld\n", name2, ln);
				return 1;
			}
			fprintf(
			    stderr, "cmp: Failed to read line %ld from file '%s': %s\n", ln, name1, strerror(errno));
			return 2;
		}
		for(ssize_t i = 0; i < MIN(nread1, nread2); i++)
		{
			if(max_bytes != 0 && pos + i >= max_bytes) return 0;
			if(line1[i] != line2[i])
			{
				if(opt_s) return 1;
				if(opt_l)
					printf("%ld %o %o\n", pos + i, line1[i], line2[i]);
				else
					printf("%s %s differ: char %zd, line %ld\n", name1, name2, i + 1, ln);
				return 1;
			}
		}
		assert(nread1 == nread2);
		pos += nread1;
		ln++;
	}
	return 0;
}
static void
usage()
{
	fprintf(stderr, "Usage: cmp [-l|-s] [-n max_bytes] file1 file2\n");
}
int
main(int argc, char *argv[])
{
	char *endptr = NULL;
	int c = -1;
	while((c = getopt(argc, argv, ":ln:s")) != -1)
	{
		switch(c)
		{
		case 'l':
			opt_l = true;
			break;
		case 's':
			opt_s = true;
			break;
		case 'n':
			errno = 0;
			max_bytes = strtoul(optarg, &endptr, 0);
			if(errno != 0)
			{
				fprintf(stderr, "cmp: Error: Failed parsing '-n %s': %s\n", optarg, strerror(errno));
				return 1;
			}
			if(endptr != NULL && endptr[0] != 0)
			{
				fprintf(
				    stderr, "cmp: Error: Non-numeric characters passed to '-n %s': %s\n", optarg, endptr);
				return 1;
			}
			break;
		case ':':
			fprintf(stderr, "cmp: Error: Missing operand for option: '-%c'\n", optopt);
			usage();
			return 1;
		case '?':
			fprintf(stderr, "cmp: Error: Unrecognised option: '-%c'\n", optopt);
			usage();
			return 1;
		default:
			abort();
		}
	}
	argc -= optind;
	argv += optind;
	if(argc != 2)
	{
		fprintf(stderr, "cmp: Expected 2 arguments, got %d arguments\n", argc);
		return 1;
	}
	if(strcmp(argv[0], argv[1]) == 0) return 0;
	assert(errno == 0);
	FILE *file1 = NULL;
	if(argv[0][0] == '-' && argv[0][1] == 0)
		file1 = stdin;
	else
	{
		file1 = fopen(argv[0], "r");
		if(file1 == NULL)
		{
			fprintf(stderr, "cmp: Error opening ‘%s’: %s\n", argv[0], strerror(errno));
			return 1;
		}
	}
	FILE *file2 = NULL;
	if(argv[1][0] == '-' && argv[1][1] == 0)
		file2 = stdin;
	else
	{
		file2 = fopen(argv[1], "r");
		if(file2 == NULL)
		{
			fprintf(stderr, "cmp: Error opening ‘%s’: %s\n", argv[1], strerror(errno));
			return 1;
		}
	}
	int ret = do_cmp(file1, argv[0], file2, argv[1]);
	fclose(file1);
	fclose(file2);
	return ret;
}