ch04-cat.c

linux编程精髓 源代码

/*
 * ch04-cat.c --- Demonstrate open(), read(), write(), close(),
 *                errno and strerror().
 */

#include <stdio.h>		/* for fprintf(), stderr, BUFSIZ */
#include <errno.h>		/* declare errno */
#include <fcntl.h>		/* for flags for open() */
#include <string.h>		/* declare strerror() */
#include <unistd.h>		/* for ssize_t */
#include <sys/types.h>
#include <sys/stat.h>		/* for mode_t */

char *myname;
int process(char *file);

/* main --- loop over file arguments */

int
main(int argc, char **argv)
{
	int i;
	int errs = 0;

	myname = argv[0];

	if (argc == 1)
		errs = process("-");
	else
		for (i = 1; i < argc; i++)
			errs += process(argv[i]);

	return (errs != 0);
}

/*
 * process --- do something with the file, in this case,
 *             send it to stdout (fd 1).
 *             Returns 0 if all OK, 1 otherwise.
 */

int
process(char *file)
{
	int fd;
	ssize_t rcount, wcount;
	char buffer[BUFSIZ];
	int errors = 0;

	if (strcmp(file, "-") == 0)
		fd = 0;
	else if ((fd = open(file, O_RDONLY)) < 0) {
		fprintf(stderr, "%s: %s: cannot open for reading: %s\n",
				myname, file, strerror(errno));
		return 1;
	}

	while ((rcount = read(fd, buffer, sizeof buffer)) > 0) {
		wcount = write(1, buffer, rcount);
		if (wcount != rcount) {
			fprintf(stderr, "%s: %s: write error: %s\n",
					myname, file, strerror(errno));
			errors++;
			break;
		}
	}

	if (rcount < 0) {
		fprintf(stderr, "%s: %s: read error: %s\n",
				myname, file, strerror(errno));
		errors++;
	}

	if (fd != 0) {
		if (close(fd) < 0) {
			fprintf(stderr, "%s: %s: close error: %s\n",
				myname, file, strerror(errno));
			errors++;
		}
	}

	return (errors != 0);
}