/*      $NetBSD: xargs.c,v 1.20 2010/12/17 11:32:57 plunky 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/cdefs.h>
#ifndef lint
__COPYRIGHT("@(#) Copyright (c) 1990, 1993\
 The Regents of the University of California.  All rights reserved.");
#if 0
static char sccsid[] = "@(#)xargs.c     8.1 (Berkeley) 6/6/93";
__FBSDID("$FreeBSD: src/usr.bin/xargs/xargs.c,v 1.62 2006/01/01 22:59:54 jmallett Exp $");
#endif
__RCSID("$NetBSD: xargs.c,v 1.20 2010/12/17 11:32:57 plunky Exp $");
#endif /* not lint */

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

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <langinfo.h>
#include <locale.h>
#include <paths.h>
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.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) __dead;
void            strnsubst(char **, const char *, const char *, size_t);
static void     waitchildren(const char *, int);

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 volatile int childerr;

extern char **environ;

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

        setprogname(argv[0]);

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

        (void)setlocale(LC_ALL, "");

        /*
         * SUSv3 says of the exec family of functions:
         *     The number of bytes available for the new process'
         *     combined argument and environment lists is {ARG_MAX}. It
         *     is implementation-defined whether null terminators,
         *     pointers, and/or any alignment bytes are included in this
         *     total.
         *
         * SUSv3 says of xargs:
         *     ... the combined argument and environment lists ...
         *     shall not exceed {ARG_MAX}-2048.
         *
         * To be conservative, we use ARG_MAX - 4K, and we do include
         * nul terminators and pointers in the calculation.
         *
         * Given that the smallest argument is 2 bytes in length, this
         * means that the number of arguments is limited to:
         *
         *       (ARG_MAX - 4K - LENGTH(env + 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:S:s:rtx")) != -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':
                        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 = 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 && 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");

        /*
         * 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) {
                        waitchildren(*argv, 1);
                        exit(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)
                        errx(1, "unterminated quote");
arg2:
                foundeof = *eofstr != '\0' &&
                    strncmp(argp, eofstr, (size_t)(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)) != 0)
                                                (void)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)
                                        errx(1, "realloc failed");
                                if (curlen == 1)
                                        (void)strcpy(inpline, argp);
                                else
                                        (void)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)
                                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;
                (void)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)
                errx(1, "malloc failed");
        tmp2 = tmp;

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

        /*
         * 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)Sflag);
                        if (repls > 0)
                                repls--;
                } else {
                        if ((*tmp = strdup(*tmp)) == NULL)
                                errx(1, "strdup failed");
                        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)
{
        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 (vfork()) {
        case -1:
                err(1, "vfork");
                /*NOTREACHED*/
        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");
                        (void)close(fd);
                }
                (void)execvp(argv[0], argv);
                childerr = errno;
                _exit(1);
        }
        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--;
                /* If we couldn't invoke the utility, exit. */
                if (childerr != 0) {
                        errno = childerr;
                        err(errno == ENOENT ? 127 : 126, "%s", name);
                }
                /*
                 * According to POSIX, we have to exit if the utility exits
                 * with a 255 status, or is interrupted by a signal. xargs
                 * is 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) != 0) {
                                rval = 123;
                        }
                } else if (WIFSIGNALED (status)) {
                        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)
{
        (void)fprintf(stderr,
"Usage: %s [-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", getprogname());
        exit(1);
}