/*      $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;
}