toys/echo.c

/* vi: set sw=4 ts=4:
 *
 * echo.c - echo supporting -n and -e.
 *
 * Copyright 2007 Rob Landley <rob@landley.net>
 *
 * See http://www.opengroup.org/onlinepubs/009695399/utilities/echo.html

USE_ECHO(NEWTOY(echo, "+en", TOYFLAG_BIN))

config ECHO
	bool "echo"
	default y
	help
	  usage: echo [-ne] [args...]

	  Write each argument to stdout, with one space between each, followed
	  by a newline.

	  -n	No trailing newline.
          -e	Process the following escape sequences:
		\\	backslash
		\a	alert (beep/flash)
		\b	backspace
		\c	Stop output here (avoids trailing newline)
		\f	form feed
		\n	newline
		\r	carriage return
		\t	horizontal tab
		\v	vertical tab
*/

#include "toys.h"

void echo_main(void)
{
	int i = 0;
	char *arg, *from = "\\abfnrtv", *to = "\\\a\b\f\n\r\t\v";

	for (;;) {
		arg = toys.optargs[i];
		if (!arg) break;
		if (i++) xputc(' ');

		// Handle -e

		if (toys.optflags&2) {
			int c, j = 0;
			for (;;) {
				c = arg[j++];
				if (!c) break;
				if (c == '\\') {
					char *found;
					int d = arg[j++];

					// handle \escapes

					if (d) {
						found = strchr(from, d);
						if (found) c = to[found-from];
						else if (d == 'c') goto done;
						else if (d == '0') {
							c = 0;
							while (arg[j]>='0' && arg[j]<='7')
								c = (c*8)+arg[j++]-'0';
						}
					}
				}
				xputc(c);
			}
		} else xprintf("%s", arg);
	}

	// Output "\n" if no -n
	if (!(toys.optflags&1)) xputc('\n');
done:
	xflush();
}