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Regarding -L, consider a line ending in unescaped white space and the next
non-empty line to form one single line, as required by XPG 4.
While here, use isblank(3) to identify white space instead of assuming
that only blank and tab are white space characters.

Geoff Clare <gwc at opengroup dot org> agrees that the standard for -L
should say "A line is considered to end with the first <newline>
unless the last character of the line is an *unescaped* <blank>;
an *unescaped* trailing <blank> signals continuation to the next
non-empty line, inclusive."  The word *unescaped* is missing from
the standard, but we regard that as a goof in the standard.

Bug noticed by, much feedback from, and "should go in now"  guenther@

/*	$OpenBSD: xargs.c,v 1.27 2010/03/25 01:03:57 schwarze Exp $	*/
/*	$FreeBSD: xargs.c,v 1.51 2003/05/03 19:09:11 obrien Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * John B. Roll Jr.
 *
 * 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.
 *
 * $xMach: xargs.c,v 1.6 2002/02/23 05:27:47 tim Exp $
 */

#include <sys/param.h>
#include <sys/wait.h>

#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <langinfo.h>
#include <locale.h>
#include <paths.h>
#include <regex.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "pathnames.h"

static void	parse_input(int, char *[]);
static void	prerun(int, char *[]);
static int	prompt(void);
static void	run(char **);
static void	usage(void);
void		strnsubst(char **, const char *, const char *, size_t);
static void	waitchildren(const char *, int);

static char **av, **bxp, **ep, **endxp, **xp;
static char *argp, *bbp, *ebp, *inpline, *p, *replstr;
static const char *eofstr;
static int count, insingle, indouble, oflag, pflag, tflag, Rflag, rval, zflag;
static int cnt, Iflag, jfound, Lflag, wasquoted, xflag, runeof = 1;
static int curprocs, maxprocs;
static size_t inpsize;

extern char **environ;

int
main(int argc, char *argv[])
{
	long arg_max;
	int ch, Jflag, nargs, nflag, nline;
	size_t linelen;
	char *endptr;

	inpline = replstr = NULL;
	ep = environ;
	eofstr = "";
	Jflag = nflag = 0;

	(void)setlocale(LC_MESSAGES, "");

	/*
	 * POSIX.2 limits the exec line length to ARG_MAX - 2K.  Running that
	 * caused some E2BIG errors, so it was changed to ARG_MAX - 4K.  Given
	 * that the smallest argument is 2 bytes in length, this means that
	 * the number of arguments is limited to:
	 *
	 *	 (ARG_MAX - 4K - LENGTH(utility + arguments)) / 2.
	 *
	 * We arbitrarily limit the number of arguments to 5000.  This is
	 * allowed by POSIX.2 as long as the resulting minimum exec line is
	 * at least LINE_MAX.  Realloc'ing as necessary is possible, but
	 * probably not worthwhile.
	 */
	nargs = 5000;
	if ((arg_max = sysconf(_SC_ARG_MAX)) == -1)
		errx(1, "sysconf(_SC_ARG_MAX) failed");
	nline = arg_max - 4 * 1024;
	while (*ep != NULL) {
		/* 1 byte for each '\0' */
		nline -= strlen(*ep++) + 1 + sizeof(*ep);
	}
	maxprocs = 1;
	while ((ch = getopt(argc, argv, "0E:I:J:L:n:oP:pR:rs:tx")) != -1)
		switch (ch) {
		case 'E':
			eofstr = optarg;
			break;
		case 'I':
			Jflag = 0;
			Iflag = 1;
			Lflag = 1;
			replstr = optarg;
			break;
		case 'J':
			Iflag = 0;
			Jflag = 1;
			replstr = optarg;
			break;
		case 'L':
			Lflag = atoi(optarg);
			break;
		case 'n':
			nflag = 1;
			if ((nargs = atoi(optarg)) <= 0)
				errx(1, "illegal argument count");
			break;
		case 'o':
			oflag = 1;
			break;
		case 'P':
			if ((maxprocs = atoi(optarg)) <= 0)
				errx(1, "max. processes must be >0");
			break;
		case 'p':
			pflag = 1;
			break;
		case 'r':
			runeof = 0;
			break;
		case 'R':
			Rflag = strtol(optarg, &endptr, 10);
			if (*endptr != '\0')
				errx(1, "replacements must be a number");
			break;
		case 's':
			nline = atoi(optarg);
			break;
		case 't':
			tflag = 1;
			break;
		case 'x':
			xflag = 1;
			break;
		case '0':
			zflag = 1;
			break;
		case '?':
		default:
			usage();
	}
	argc -= optind;
	argv += optind;

	if (!Iflag && Rflag)
		usage();
	if (Iflag && !Rflag)
		Rflag = 5;
	if (xflag && !nflag)
		usage();
	if (Iflag || Lflag)
		xflag = 1;
	if (replstr != NULL && *replstr == '\0')
		errx(1, "replstr may not be empty");

	/*
	 * Allocate pointers for the utility name, the utility arguments,
	 * the maximum arguments to be read from stdin and the trailing
	 * NULL.
	 */
	linelen = 1 + argc + nargs + 1;
	if ((av = bxp = calloc(linelen, sizeof(char **))) == NULL)
		err(1, NULL);

	/*
	 * Use the user's name for the utility as argv[0], just like the
	 * shell.  Echo is the default.  Set up pointers for the user's
	 * arguments.
	 */
	if (*argv == NULL)
		cnt = strlen(*bxp++ = _PATH_ECHO);
	else {
		do {
			if (Jflag && strcmp(*argv, replstr) == 0) {
				char **avj;
				jfound = 1;
				argv++;
				for (avj = argv; *avj; avj++)
					cnt += strlen(*avj) + 1;
				break;
			}
			cnt += strlen(*bxp++ = *argv) + 1;
		} while (*++argv != NULL);
	}

	/*
	 * Set up begin/end/traversing pointers into the array.  The -n
	 * count doesn't include the trailing NULL pointer, so the malloc
	 * added in an extra slot.
	 */
	endxp = (xp = bxp) + nargs;

	/*
	 * Allocate buffer space for the arguments read from stdin and the
	 * trailing NULL.  Buffer space is defined as the default or specified
	 * space, minus the length of the utility name and arguments.  Set up
	 * begin/end/traversing pointers into the array.  The -s count does
	 * include the trailing NULL, so the malloc didn't add in an extra
	 * slot.
	 */
	nline -= cnt;
	if (nline <= 0)
		errx(1, "insufficient space for command");

	if ((bbp = malloc((size_t)(nline + 1))) == NULL)
		err(1, NULL);
	ebp = (argp = p = bbp) + nline - 1;
	for (;;)
		parse_input(argc, argv);
}

static void
parse_input(int argc, char *argv[])
{
	int hasblank = 0;
	static int hadblank = 0;
	int ch, foundeof = 0;
	char **avj;

	ch = getchar();
	if (isblank(ch)) {
		/* Quotes escape tabs and spaces. */
		if (insingle || indouble)
			goto addch;
		hasblank = 1;
		if (zflag)
			goto addch;
		goto arg2;
	}

	switch (ch) {
	case EOF:
		/* No arguments since last exec. */
		if (p == bbp) {
			if (runeof)
				prerun(0, av);
			waitchildren(*argv, 1);
			exit(rval);
		}
		goto arg1;
	case '\0':
		if (zflag)
			goto arg2;
		goto addch;
	case '\n':
		hasblank = 1;
		if (hadblank == 0)
			count++;
		if (zflag)
			goto addch;

		/* Quotes do not escape newlines. */
arg1:		if (insingle || indouble)
			errx(1, "unterminated quote");
arg2:
		foundeof = *eofstr != '\0' &&
		    strcmp(argp, eofstr) == 0;

		/* Do not make empty args unless they are quoted */
		if ((argp != p || wasquoted) && !foundeof) {
			*p++ = '\0';
			*xp++ = argp;
			if (Iflag) {
				size_t curlen;

				if (inpline == NULL)
					curlen = 0;
				else {
					/*
					 * If this string is not zero
					 * length, append a space for
					 * separation before the next
					 * argument.
					 */
					if ((curlen = strlen(inpline)))
						strlcat(inpline, " ", inpsize);
				}
				curlen++;
				/*
				 * Allocate enough to hold what we will
				 * be holding in a second, and to append
				 * a space next time through, if we have
				 * to.
				 */
				inpsize = curlen + 2 + strlen(argp);
				inpline = realloc(inpline, inpsize);
				if (inpline == NULL)
					errx(1, "realloc failed");
				if (curlen == 1)
					strlcpy(inpline, argp, inpsize);
				else
					strlcat(inpline, argp, inpsize);
			}
		}

		/*
		 * If max'd out on args or buffer, or reached EOF,
		 * run the command.  If xflag and max'd out on buffer
		 * but not on args, object.  Having reached the limit
		 * of input lines, as specified by -L is the same as
		 * maxing out on arguments.
		 */
		if (xp == endxp || p > ebp || ch == EOF ||
		    (Lflag <= count && xflag) || foundeof) {
			if (xflag && xp != endxp && p > ebp)
				errx(1, "insufficient space for arguments");
			if (jfound) {
				for (avj = argv; *avj; avj++)
					*xp++ = *avj;
			}
			prerun(argc, av);
			if (ch == EOF || foundeof) {
				waitchildren(*argv, 1);
				exit(rval);
			}
			p = bbp;
			xp = bxp;
			count = 0;
		}
		argp = p;
		wasquoted = 0;
		break;
	case '\'':
		if (indouble || zflag)
			goto addch;
		insingle = !insingle;
		wasquoted = 1;
		break;
	case '"':
		if (insingle || zflag)
			goto addch;
		indouble = !indouble;
		wasquoted = 1;
		break;
	case '\\':
		if (zflag)
			goto addch;
		/* Backslash escapes anything, is escaped by quotes. */
		if (!insingle && !indouble && (ch = getchar()) == EOF)
			errx(1, "backslash at EOF");
		/* FALLTHROUGH */
	default:
addch:		if (p < ebp) {
			*p++ = ch;
			break;
		}

		/* If only one argument, not enough buffer space. */
		if (bxp == xp)
			errx(1, "insufficient space for argument");
		/* Didn't hit argument limit, so if xflag object. */
		if (xflag)
			errx(1, "insufficient space for arguments");

		if (jfound) {
			for (avj = argv; *avj; avj++)
				*xp++ = *avj;
		}
		prerun(argc, av);
		xp = bxp;
		cnt = ebp - argp;
		memcpy(bbp, argp, (size_t)cnt);
		p = (argp = bbp) + cnt;
		*p++ = ch;
		break;
	}
	hadblank = hasblank;
}

/*
 * Do things necessary before run()'ing, such as -I substitution,
 * and then call run().
 */
static void
prerun(int argc, char *argv[])
{
	char **tmp, **tmp2, **avj;
	int repls;

	repls = Rflag;
	runeof = 0;

	if (argc == 0 || repls == 0) {
		*xp = NULL;
		run(argv);
		return;
	}

	avj = argv;

	/*
	 * Allocate memory to hold the argument list, and
	 * a NULL at the tail.
	 */
	tmp = calloc(argc + 1, sizeof(char**));
	if (tmp == NULL)
		err(1, NULL);
	tmp2 = tmp;

	/*
	 * Save the first argument and iterate over it, we
	 * cannot do strnsubst() to it.
	 */
	if ((*tmp++ = strdup(*avj++)) == NULL)
		err(1, NULL);

	/*
	 * For each argument to utility, if we have not used up
	 * the number of replacements we are allowed to do, and
	 * if the argument contains at least one occurrence of
	 * replstr, call strnsubst(), else just save the string.
	 * Iterations over elements of avj and tmp are done
	 * where appropriate.
	 */
	while (--argc) {
		*tmp = *avj++;
		if (repls && strstr(*tmp, replstr) != NULL) {
			strnsubst(tmp++, replstr, inpline, (size_t)255);
			if (repls > 0)
				repls--;
		} else {
			if ((*tmp = strdup(*tmp)) == NULL)
				err(1, NULL);
			tmp++;
		}
	}

	/*
	 * Run it.
	 */
	*tmp = NULL;
	run(tmp2);

	/*
	 * Walk from the tail to the head, free along the way.
	 */
	for (; tmp2 != tmp; tmp--)
		free(*tmp);
	/*
	 * Now free the list itself.
	 */
	free(tmp2);

	/*
	 * Free the input line buffer, if we have one.
	 */
	if (inpline != NULL) {
		free(inpline);
		inpline = NULL;
	}
}

static void
run(char **argv)
{
	pid_t pid;
	int fd;
	char **avec;

	/*
	 * If the user wants to be notified of each command before it is
	 * executed, notify them.  If they want the notification to be
	 * followed by a prompt, then prompt them.
	 */
	if (tflag || pflag) {
		(void)fprintf(stderr, "%s", *argv);
		for (avec = argv + 1; *avec != NULL; ++avec)
			(void)fprintf(stderr, " %s", *avec);
		/*
		 * If the user has asked to be prompted, do so.
		 */
		if (pflag)
			/*
			 * If they asked not to exec, return without execution
			 * but if they asked to, go to the execution.  If we
			 * could not open their tty, break the switch and drop
			 * back to -t behaviour.
			 */
			switch (prompt()) {
			case 0:
				return;
			case 1:
				goto exec;
			case 2:
				break;
			}
		(void)fprintf(stderr, "\n");
		(void)fflush(stderr);
	}
exec:
	switch (pid = vfork()) {
	case -1:
		err(1, "vfork");
	case 0:
		if (oflag) {
			if ((fd = open(_PATH_TTY, O_RDONLY)) == -1) {
				warn("can't open /dev/tty");
				_exit(1);
			}
		} else {
			fd = open(_PATH_DEVNULL, O_RDONLY);
		}
		if (fd > STDIN_FILENO) {
			if (dup2(fd, STDIN_FILENO) != 0) {
				warn("can't dup2 to stdin");
				_exit(1);
			}
			close(fd);
		}
		execvp(argv[0], argv);
		warn("%s", argv[0]);
		_exit(errno == ENOENT ? 127 : 126);
	}
	curprocs++;
	waitchildren(*argv, 0);
}

static void
waitchildren(const char *name, int waitall)
{
	pid_t pid;
	int status;

	while ((pid = waitpid(-1, &status, !waitall && curprocs < maxprocs ?
	    WNOHANG : 0)) > 0) {
		curprocs--;
		/*
		 * According to POSIX, we have to exit if the utility exits
		 * with a 255 status, or is interrupted by a signal.
		 * We are allowed to return any exit status between 1 and
		 * 125 in these cases, but we'll use 124 and 125, the same
		 * values used by GNU xargs.
		 */
		if (WIFEXITED(status)) {
			if (WEXITSTATUS(status) == 255) {
				warnx("%s exited with status 255", name);
				exit(124);
			} else if (WEXITSTATUS(status) == 127 ||
			    WEXITSTATUS(status) == 126) {
				exit(WEXITSTATUS(status));
			} else if (WEXITSTATUS(status) != 0) {
				rval = 123;
			}
		} else if (WIFSIGNALED(status)) {
			if (WTERMSIG(status) != SIGPIPE) {
				if (WTERMSIG(status) < NSIG)
					warnx("%s terminated by SIG%s", name,
					    sys_signame[WTERMSIG(status)]);
				else
					warnx("%s terminated by signal %d",
					    name, WTERMSIG(status));
			}
			exit(125);
		}
	}
	if (pid == -1 && errno != ECHILD)
		err(1, "waitpid");
}

/*
 * Prompt the user about running a command.
 */
static int
prompt(void)
{
	regex_t cre;
	size_t rsize;
	int match;
	char *response;
	FILE *ttyfp;

	if ((ttyfp = fopen(_PATH_TTY, "r")) == NULL)
		return (2);	/* Indicate that the TTY failed to open. */
	(void)fprintf(stderr, "?...");
	(void)fflush(stderr);
	if ((response = fgetln(ttyfp, &rsize)) == NULL ||
	    regcomp(&cre, nl_langinfo(YESEXPR), REG_BASIC) != 0) {
		(void)fclose(ttyfp);
		return (0);
	}
	response[rsize - 1] = '\0';
	match = regexec(&cre, response, 0, NULL, 0);
	(void)fclose(ttyfp);
	regfree(&cre);
	return (match == 0);
}

static void
usage(void)
{
	fprintf(stderr,
"usage: xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr]\n"
"             [-L number] [-n number [-x]] [-P maxprocs] [-s size]\n"
"             [utility [argument ...]]\n");
	exit(1);
}