cat.c

/*-
 * Copyright (c) 2014 Robert Clausecker <[email protected]>
 */

#define _POSIX_C_SOURCE 200809L
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include "err.h"

extern int	main(int, char*[]);
static void	output_file(const char*);

/*
 * Implementation of cat(1) according to IEEE Std 1003.1, 2013 Edition.
 * This implementation does not support any extensions beyond the standard.
 */
extern int
main(int argc, char *argv[])
{
	int optchar;
	int i;

	setprogname(argv[0]);

	while ((optchar = getopt(argc, argv, "u")) != -1)
		switch (optchar) {
		case 'u':
			/* buffering behaves like -u by default */
			break;
		case '?':
			return (2);
		}

	if (optind == argc) {
		output_file("-");
		return (0);
	}

	for (i = optind; i < argc; i++)
		output_file(argv[i]);

	return (0);
}

/*
 * Copy the contents of the file filename to stdout. stdin is copied to stdout
 * of filename is "-". If an error occurs, this function prints a diagnostic to
 * stderr and returns 1. 0 is returned on success.
 */
static void
output_file(const char *filename)
{
	static char iobuf[BUFSIZ];
	int fd;
	ssize_t read_count, write_count;

	if (strcmp(filename, "-") == 0)
		fd = STDIN_FILENO;
	else {
		fd = open(filename, O_RDONLY);
		if (fd == -1)
			/* LOCALIZE */
			err(1, "Cannot open file %s", filename);
	}

	while ((read_count = read(fd, iobuf, sizeof(iobuf))) > 0) {
		write_count = write(STDOUT_FILENO, iobuf, read_count);
		if (write_count < read_count)
			/* LOCALIZE */
			err(1, "Error writing to stdout");
	}

	if (read_count < 0)
		/* LOCALIZE */
		err(1, "Error reading file %s", filename);

	if (fd != STDIN_FILENO && close(fd) != 0)
		/* LOCALIZE */
		err(1, "Error closing file %s", filename);
}