utils

cat.c (1505B)

// Collection of Unix tools, comparable to coreutils
// SPDX-FileCopyrightText: 2017-2022 Haelwenn (lanodan) Monnier <contact+utils@hacktivis.me>
// SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only
#define _POSIX_C_SOURCE 200809L
#include <errno.h>  /* errno */
#include <fcntl.h>  /* open(), O_RDONLY */
#include <stdio.h>  /* fprintf(), BUFSIZ */
#include <string.h> /* strerror(), strncmp() */
#include <unistd.h> /* read(), write(), close() */
int
concat(int fd, const char *fdname)
{
	ssize_t c;
	char buf[BUFSIZ];
	while((c = read(fd, buf, sizeof(buf))) > 0)
	{
		if(write(1, buf, (size_t)c) < 0)
		{
			fprintf(stderr, "\nError writing: %s\n", strerror(errno));
			return 1;
		}
	}
	if(c < 0)
	{
		fprintf(stderr, "\nError reading ‘%s’: %s\n", fdname, strerror(errno));
		return 1;
	}
	return 0;
}
int
main(int argc, char *argv[])
{
	if(argc <= 1)
	{
		return concat(0, "<stdin>");
	}
	for(int argi = 1; argi < argc; argi++)
	{
		if(strncmp(argv[argi], "-", 2) == 0)
		{
			if(concat(0, "<stdin>") != 0)
			{
				return 1;
			}
		}
		else if(strncmp(argv[argi], "--", 3) == 0)
		{
			continue;
		}
		else
		{
			int fd = open(argv[argi], O_RDONLY);
			if(fd < 0)
			{
				fprintf(stderr, "\nError opening ‘%s’: %s\n", argv[argi], strerror(errno));
				return 1;
			}
			if(concat(fd, argv[argi]) != 0)
			{
				return 1;
			}
			if(close(fd) < 0)
			{
				fprintf(stderr, "\nError closing ‘%s’: %s\n", argv[argi], strerror(errno));
				return 1;
			}
		}
	}
	return 0;
}