/*	$NetBSD: echo.c,v 1.15 2021/05/18 21:39:06 kre Exp $	*/

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Kenneth Almquist.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)echo.c	8.1 (Berkeley) 5/31/93
 */

/*
 * Echo command.
 *
 * echo is steeped in tradition - several of them!
 * netbsd has supported 'echo [-n | -e] args' in spite of -e not being
 * documented anywhere.
 * Posix requires that -n be supported, output from strings containing
 * \ is implementation defined
 * The Single Unix Spec requires that \ escapes be treated as if -e
 * were set, but that -n not be treated as an option.
 * (ksh supports 'echo [-eEn] args', but not -- so that it is actually
 * impossible to actually output '-n')
 *
 * It is suggested that 'printf "%b" "string"' be used to get \ sequences
 * expanded.  printf is now a builtin of netbsd's sh and csh.
 */

#include <sys/cdefs.h>
__RCSID("$NetBSD: echo.c,v 1.15 2021/05/18 21:39:06 kre Exp $");

#define main echocmd

#include "bltin.h"

int
main(int argc, char **argv)
{
	char **ap;
	char *p;
	char c;
	int count;
	int nflag = 0;
	int eflag = 0;

	clearerr(stdout);

	ap = argv;
	if (argc)
		ap++;

	if ((p = *ap) != NULL) {
		if (equal(p, "-n")) {
			nflag = 1;
			ap++;
		} else if (equal(p, "-e")) {
			eflag = 1;
			ap++;
		}
	}

	while ((p = *ap++) != NULL) {
		while ((c = *p++) != '\0') {
			if (c == '\\' && eflag) {
				switch (*p++) {
				case 'a':  c = '\a';  break;	/* bell */
				case 'b':  c = '\b';  break;
				case 'c':  return 0;		/* exit */
				case 'e':  c =  033;  break;	/* escape */
				case 'f':  c = '\f';  break;
				case 'n':  c = '\n';  break;
				case 'r':  c = '\r';  break;
				case 't':  c = '\t';  break;
				case 'v':  c = '\v';  break;
				case '\\':  break;		/* c = '\\' */
				case '0':
					c = 0;
					count = 3;
					while (--count >= 0 && (unsigned)(*p - '0') < 8)
						c = (c << 3) + (*p++ - '0');
					break;
				default:
					/* Output the '/' and char following */
					p--;
					break;
				}
			}
			putchar(c);
		}
		if (*ap)
			putchar(' ');
	}
	if (! nflag)
		putchar('\n');
	fflush(stdout);
	if (ferror(stdout)) {
		clearerr(stdout);
		err(1, "write error");
	}
	return 0;
}
