/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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 $
 */

#if 0
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1990, 1993\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)xargs.c	8.1 (Berkeley) 6/6/93";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/limits.h>
#include <sys/resource.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <langinfo.h>
#include <locale.h>
#include <paths.h>
#include <regex.h>
#include <stdbool.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);
bool		strnsubst(char **, const char *, const char *, size_t);
static pid_t	xwait(int block, int *status);
static void	xexit(const char *, const int);
static void	waitchildren(const char *, int);
static void	pids_init(void);
static int	pids_empty(void);
static int	pids_full(void);
static void	pids_add(pid_t pid);
static int	pids_remove(pid_t pid);
static int	findslot(pid_t pid);
static int	findfreeslot(void);
static void	clearslot(int slot);

static char echo[] = _PATH_ECHO;
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, Sflag, wasquoted, xflag;
static int curprocs, maxprocs;
static pid_t *childpids;

static volatile int childerr;

extern char **environ;

static const char *optstr = "+0E:I:J:L:n:oP:pR:S:s:rtx";

static const struct option long_options[] =
{
	{"exit",		no_argument,		NULL,	'x'},
	{"interactive",		no_argument,		NULL,	'p'},
	{"max-args",		required_argument,	NULL,	'n'},
	{"max-chars",		required_argument,	NULL,	's'},
	{"max-procs",		required_argument,	NULL,	'P'},
	{"no-run-if-empty",	no_argument,		NULL,	'r'},
	{"null",		no_argument,		NULL,	'0'},
	{"verbose",		no_argument,		NULL,	't'},

	{NULL,			no_argument,		NULL,	0},
};

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

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

	(void)setlocale(LC_ALL, "");

	/*
	 * 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_long(argc, argv, optstr, long_options, NULL)) != -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 = strtonum(optarg, 0, INT_MAX, &errstr);
			if (errstr)
				errx(1, "-L %s: %s", optarg, errstr);
			break;
		case 'n':
			nflag = 1;
			nargs = strtonum(optarg, 1, INT_MAX, &errstr);
			if (errstr)
				errx(1, "-n %s: %s", optarg, errstr);
			break;
		case 'o':
			oflag = 1;
			break;
		case 'P':
			maxprocs = strtonum(optarg, 0, INT_MAX, &errstr);
			if (errstr)
				errx(1, "-P %s: %s", optarg, errstr);
			if (getrlimit(RLIMIT_NPROC, &rl) != 0)
				errx(1, "getrlimit failed");
			if (maxprocs == 0 || maxprocs > rl.rlim_cur)
				maxprocs = rl.rlim_cur;
			break;
		case 'p':
			pflag = 1;
			break;
		case 'R':
			Rflag = strtol(optarg, &endptr, 10);
			if (*endptr != '\0')
				errx(1, "replacements must be a number");
			break;
		case 'r':
			/* GNU compatibility */
			break;
		case 'S':
			Sflag = strtoul(optarg, &endptr, 10);
			if (*endptr != '\0')
				errx(1, "replsize must be a number");
			break;
		case 's':
			nline = strtonum(optarg, 0, INT_MAX, &errstr);
			if (errstr)
				errx(1, "-s %s: %s", optarg, errstr);
			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 && Sflag)
		usage();
	if (Iflag && !Rflag)
		Rflag = 5;
	if (Iflag && !Sflag)
		Sflag = 255;
	if (xflag && !nflag)
		usage();
	if (Iflag || Lflag)
		xflag = 1;
	if (replstr != NULL && *replstr == '\0')
		errx(1, "replstr may not be empty");

	pids_init();

	/*
	 * 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 = malloc(linelen * sizeof(char *))) == NULL)
		errx(1, "malloc failed");

	/*
	 * 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++ = 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)
		errx(1, "malloc failed");
	ebp = (argp = p = bbp) + nline - 1;
	for (;;)
		parse_input(argc, argv);
}

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

	foundeof = 0;

	switch (ch = getchar()) {
	case EOF:
		/* No arguments since last exec. */
		if (p == bbp)
			xexit(*av, rval);
		goto arg1;
	case ' ':
	case '\t':
		/* Quotes escape tabs and spaces. */
		if (insingle || indouble || zflag)
			goto addch;
		goto arg2;
	case '\0':
		if (zflag) {
			/*
			 * Increment 'count', so that nulls will be treated
			 * as end-of-line, as well as end-of-argument.  This
			 * is needed so -0 works properly with -I and -L.
			 */
			count++;
			goto arg2;
		}
		goto addch;
	case '\n':
		if (zflag)
			goto addch;
		count++;	    /* Indicate end-of-line (used by -L) */

		/* Quotes do not escape newlines. */
arg1:		if (insingle || indouble) {
			warnx("unterminated quote");
			xexit(*av, 1);
		}
arg2:
		foundeof = *eofstr != '\0' &&
		    strncmp(argp, eofstr, p - argp) == 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)))
						strcat(inpline, " ");
				}
				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.
				 */
				inpline = realloc(inpline, curlen + 2 +
				    strlen(argp));
				if (inpline == NULL) {
					warnx("realloc failed");
					xexit(*av, 1);
				}
				if (curlen == 1)
					strcpy(inpline, argp);
				else
					strcat(inpline, argp);
			}
		}

		/*
		 * 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) {
				warnx("insufficient space for arguments");
				xexit(*av, 1);
			}
			if (jfound) {
				for (avj = argv; *avj; avj++)
					*xp++ = *avj;
			}
			prerun(argc, av);
			if (ch == EOF || foundeof)
				xexit(*av, 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) {
			warnx("backslash at EOF");
			xexit(*av, 1);
		}
		/* FALLTHROUGH */
	default:
addch:		if (p < ebp) {
			*p++ = ch;
			break;
		}

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

		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;
	}
}

/*
 * 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;

	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 = malloc((argc + 1) * sizeof(char *));
	if (tmp == NULL) {
		warnx("malloc failed");
		xexit(*argv, 1);
	}
	tmp2 = tmp;

	/*
	 * Save the first argument and iterate over it, we
	 * cannot do strnsubst() to it.
	 */
	if ((*tmp++ = strdup(*avj++)) == NULL) {
		warnx("strdup failed");
		xexit(*argv, 1);
	}

	/*
	 * 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) {
			if (strnsubst(tmp++, replstr, inpline, (size_t)Sflag)) {
				warnx("comamnd line cannot be assembled, too long");
				xexit(*argv, 1);
			}
			if (repls > 0)
				repls--;
		} else {
			if ((*tmp = strdup(*tmp)) == NULL) {
				warnx("strdup failed");
				xexit(*argv, 1);
			}
			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:
	childerr = 0;
	switch (pid = vfork()) {
	case -1:
		warn("vfork");
		xexit(*argv, 1);
	case 0:
		if (oflag) {
			if ((fd = open(_PATH_TTY, O_RDONLY)) == -1)
				err(1, "can't open /dev/tty");
		} else {
			fd = open(_PATH_DEVNULL, O_RDONLY);
		}
		if (fd > STDIN_FILENO) {
			if (dup2(fd, STDIN_FILENO) != 0)
				err(1, "can't dup2 to stdin");
			close(fd);
		}
		execvp(argv[0], argv);
		childerr = errno;
		_exit(1);
	}
	pids_add(pid);
	waitchildren(*argv, 0);
}

/*
 * Wait for a tracked child to exit and return its pid and exit status.
 *
 * Ignores (discards) all untracked child processes.
 * Returns -1 and sets errno to ECHILD if no tracked children exist.
 * If block is set, waits indefinitely for a child process to exit.
 * If block is not set and no children have exited, returns 0 immediately.
 */
static pid_t
xwait(int block, int *status) {
	pid_t pid;

	if (pids_empty()) {
		errno = ECHILD;
		return (-1);
	}

	while ((pid = waitpid(-1, status, block ? 0 : WNOHANG)) > 0)
		if (pids_remove(pid))
			break;

	return (pid);
}

static void
xexit(const char *name, const int exit_code) {
	waitchildren(name, 1);
	exit(exit_code);
}

static void
waitchildren(const char *name, int waitall)
{
	pid_t pid;
	int status;
	int cause_exit = 0;

	while ((pid = xwait(waitall || pids_full(), &status)) > 0) {
		/*
		 * If we couldn't invoke the utility or if utility exited
		 * because of a signal or with a value of 255, warn (per
		 * POSIX), and then wait until all other children have
		 * exited before exiting 1-125. POSIX requires us to stop
		 * reading if child exits because of a signal or with 255,
		 * but it does not require us to exit immediately; waiting
		 * is preferable to orphaning.
		 */
		if (childerr != 0 && cause_exit == 0) {
			errno = childerr;
			waitall = 1;
			cause_exit = errno == ENOENT ? 127 : 126;
			warn("%s", name);
		} else if (WIFSIGNALED(status)) {
			waitall = cause_exit = 1;
			warnx("%s: terminated with signal %d; aborting",
			    name, WTERMSIG(status));
		} else if (WEXITSTATUS(status) == 255) {
			waitall = cause_exit = 1;
			warnx("%s: exited with status 255; aborting", name);
		} else if (WEXITSTATUS(status))
 			rval = 1;
	}

 	if (cause_exit)
		exit(cause_exit);
	if (pid == -1 && errno != ECHILD)
		err(1, "waitpid");
}

#define	NOPID	(0)

static void
pids_init(void)
{
	int i;

	if ((childpids = malloc(maxprocs * sizeof(*childpids))) == NULL)
		errx(1, "malloc failed");

	for (i = 0; i < maxprocs; i++)
		clearslot(i);
}

static int
pids_empty(void)
{

	return (curprocs == 0);
}

static int
pids_full(void)
{

	return (curprocs >= maxprocs);
}

static void
pids_add(pid_t pid)
{
	int slot;

	slot = findfreeslot();
	childpids[slot] = pid;
	curprocs++;
}

static int
pids_remove(pid_t pid)
{
	int slot;

	if ((slot = findslot(pid)) < 0)
		return (0);

	clearslot(slot);
	curprocs--;
	return (1);
}

static int
findfreeslot(void)
{
	int slot;

	if ((slot = findslot(NOPID)) < 0)
		errx(1, "internal error: no free pid slot");
	return (slot);
}

static int
findslot(pid_t pid)
{
	int slot;

	for (slot = 0; slot < maxprocs; slot++)
		if (childpids[slot] == pid)
			return (slot);
	return (-1);
}

static void
clearslot(int slot)
{

	childpids[slot] = NOPID;
}

/*
 * 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_EXTENDED) != 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 [-0opt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]]\n"
"             [-J replstr] [-L number] [-n number [-x]] [-P maxprocs]\n"
"             [-s size] [utility [argument ...]]\n");
	exit(1);
}