micro-utils/coreutils/cat.c

#include <fcntl.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>

void cat(const int fd) {
	char buf[8096];
	ssize_t len;

	while ((len = read(fd, buf, sizeof(buf))) > 0)
		if (write(1, buf, len) != len)
			fprintf(stderr, "cat: write error copying\n");
}

int main(const int argc, const char **argv) {
	if (argc == 1)
		cat(STDIN_FILENO);

	else {
		for (int i = 1; i < argc; i++) {
			if (argv[i][0] == '-') {
				if (argv[i][1])
					continue;

				else
					cat(STDIN_FILENO);

				continue;
			}

			int fd = open(argv[i], O_RDONLY);
			if (fd < 0) {
				fprintf(stderr, "cat: %s %s\n", argv[i], strerror(errno));
				return 1;
			}

			cat(fd);
			close(fd);
		}
	}

	return 0;
}