/*      $NetBSD: redir.c,v 1.77 2025/12/10 21:33:02 andvar 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.
 */

#include <sys/cdefs.h>
#ifndef lint
#if 0
static char sccsid[] = "@(#)redir.c     8.2 (Berkeley) 5/4/95";
#else
__RCSID("$NetBSD: redir.c,v 1.77 2025/12/10 21:33:02 andvar Exp $");
#endif
#endif /* not lint */

#include <sys/types.h>
#include <sys/param.h>  /* PIPE_BUF */
#include <sys/stat.h>
#include <signal.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>

/*
 * Code for dealing with input/output redirection.
 */

#include "main.h"
#include "builtins.h"
#include "shell.h"
#include "nodes.h"
#include "jobs.h"
#include "options.h"
#include "expand.h"
#include "redir.h"
#include "output.h"
#include "memalloc.h"
#include "mystring.h"
#include "error.h"
#include "show.h"


#define CLOSED -1               /* fd was not open before redir */

#ifndef PIPE_BUF
# define PIPESIZE 4096          /* amount of buffering in a pipe */
#else
# define PIPESIZE PIPE_BUF
#endif

#ifndef FD_CLOEXEC
# define FD_CLOEXEC     1       /* well known from before there was a name */
#endif

#ifndef F_DUPFD_CLOEXEC
#define F_DUPFD_CLOEXEC F_DUPFD
#define CLOEXEC(fd)     (fcntl((fd), F_SETFD,                           \
                             (fcntl_int)(fcntl((fd), F_GETFD) | FD_CLOEXEC)))
#else
#define CLOEXEC(fd)     __nothing
#endif

/* yes, this is correct, bizarre parens and all -- used only as a cast */
#define fcntl_int       void *)(intptr_t
#undef  fcntl_int
#define fcntl_int       int


MKINIT
struct renamelist {
        struct renamelist *next;
        int orig;
        int into;
        int cloexec;    /* orig had FD_CLOEXEC set (into always does) */
};

MKINIT
struct redirtab {
        struct redirtab *next;
        struct renamelist *renamed;
};


MKINIT struct redirtab *redirlist;

/*
 * We keep track of whether or not fd0 has been redirected.  This is for
 * background commands, where we want to redirect fd0 to /dev/null only
 * if it hasn't already been redirected.
 */
STATIC int fd0_redirected = 0;

/*
 * And also where to put internal use fds that should be out of the
 * way of user defined fds (normally)
 */
STATIC int big_sh_fd = 0;
STATIC int biggest_sh_fd = 2;

STATIC const struct renamelist *is_renamed(const struct renamelist *, int);
STATIC void fd_rename(struct redirtab *, int, int, int);
STATIC int * saved_redirected_fd(int);
STATIC void free_rl(struct redirtab *, int);
STATIC void openredirect(union node *, char[10], int);
STATIC int openhere(const union node *);
STATIC int copyfd(int, int, int, int);
STATIC void find_big_fd(void);


struct shell_fds {              /* keep track of internal shell fds */
        struct shell_fds *nxt;
        void (*cb)(int, int);
        int fd;
};

STATIC struct shell_fds *sh_fd_list;

STATIC int pick_new_fd(int);
STATIC void renumber_sh_fd(struct shell_fds *);
STATIC struct shell_fds *sh_fd(int);

STATIC const struct renamelist *
is_renamed(const struct renamelist *rl, int fd)
{
        while (rl != NULL) {
                if (rl->orig == fd)
                        return rl;
                rl = rl->next;
        }
        return NULL;
}

STATIC int *
saved_redirected_fd(int fd)
{
        struct redirtab *rt;
        struct renamelist *rl;

        for (rt = redirlist; rt != NULL; rt = rt->next) {
                for (rl =  rt->renamed; rl != NULL; rl = rl->next) {
                        if (rl->into == fd)
                                return &rl->into;
                }
        }
        return NULL;
}

STATIC void
free_rl(struct redirtab *rt, int reset)
{
        struct renamelist *rl, *rn = rt->renamed;

        while ((rl = rn) != NULL) {
                rn = rl->next;

                if (rl->orig == 0)
                        fd0_redirected--;

                VTRACE(DBG_REDIR, ("popredir %d%s: %s",
                    rl->orig, rl->orig==0 ? " (STDIN)" : "",
                    reset == POPREDIR_UNDO ? "" :
                    reset == POPREDIR_PERMANENT ? "make permanent" :
                                             "no reset\n"));

                switch (reset) {
                case POPREDIR_UNDO:
                        if (rl->into < 0) {
                                VTRACE(DBG_REDIR, (" closed\n"));
                                close(rl->orig);
                        } else {
                                VTRACE(DBG_REDIR,
                                    (" from %d%s\n", rl->into,
                                       rl->cloexec ? " (colexec)" : ""));
                                copyfd(rl->into, rl->orig, rl->cloexec, 1);
                        }
                        break;

                case POPREDIR_PERMANENT:
                        if (rl->into < 0) {
                                VTRACE(DBG_REDIR, (" was closed\n"));
                                /* nothing to do */
                        } else {
                                VTRACE(DBG_REDIR,
                                    (" close savefd %d\n", rl->into));
                                close(rl->into);
                        }
                        break;

                default:
                        /* nothing to do */
                        break;
                }
                ckfree(rl);
        }
        rt->renamed = NULL;
}

STATIC void
fd_rename(struct redirtab *rt, int from, int to, int cloexec)
{
        /* XXX someday keep a short list (8..10) of freed renamelists XXX */
        struct renamelist *rl = ckmalloc(sizeof(struct renamelist));

        /*
         * Note this list is operated as LIFO so saved fd's are
         * undone in the opposite order to that they were saved
         * (needed to ensure correct results)
         */
        rl->next = rt->renamed;
        rt->renamed = rl;

        rl->orig = from;
        rl->into = to;
        rl->cloexec = cloexec;
}

/*
 * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
 * old file descriptors are stashed away so that the redirection can be
 * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
 * standard output, and the standard error if it becomes a duplicate of
 * stdout, is saved in memory.
 */

void
redirect(union node *redir, int flags)
{
        union node *n;
        struct redirtab *sv = NULL;
        int i;
        int fd;
        char memory[10];        /* file descriptors to write to memory */

        CTRACE(DBG_REDIR, ("redirect(F=0x%x):%s\n", flags, redir?"":" NONE"));

        for (i = 10 ; --i >= 0 ; )
                memory[i] = 0;
        memory[1] = flags & REDIR_BACKQ;
        if (flags & REDIR_PUSH) {
                /*
                 * We don't have to worry about REDIR_VFORK here, as
                 * flags & REDIR_PUSH is never true if REDIR_VFORK is set.
                 */
                sv = ckmalloc(sizeof (struct redirtab));
                sv->renamed = NULL;
                sv->next = redirlist;
                redirlist = sv;
        }
        for (n = redir ; n ; n = n->nfile.next) {
                int *renamed;

                fd = n->nfile.fd;
                VTRACE(DBG_REDIR, ("redir %d (max=%d limit=%ld) ",
                    fd, max_user_fd, user_fd_limit));
                if (fd < user_fd_limit && fd > max_user_fd)
                        max_user_fd = fd;
                if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
                    n->ndup.dupfd == fd) {
                        VTRACE(DBG_REDIR, ("!cloexec\n"));
                        if (sh_fd(fd) != NULL ||
                            saved_redirected_fd(fd) != NULL)
                                error("fd %d: %s", fd, strerror(EBADF));
                        /* redirect from/to same file descriptor */
                        /* make sure it stays open */
                        if (fcntl(fd, F_SETFD, (fcntl_int)0) < 0)
                                error("fd %d: %s", fd, strerror(errno));
                        continue;
                }
                if ((renamed = saved_redirected_fd(fd)) != NULL) {
                        int to = pick_new_fd(fd);

                        VTRACE(DBG_REDIR,
                            ("redirect: moved holding fd %d to %d\n", fd, to));
                        *renamed = to;
                        if (to != fd)   /* always... */
                                (void)close(fd);
                }
                renumber_sh_fd(sh_fd(fd));

                if ((flags & REDIR_PUSH) && !is_renamed(sv->renamed, fd)) {
                        int bigfd;
                        int cloexec;

                        cloexec = fcntl(fd, F_GETFD);
                        if (cloexec >= 0)
                                cloexec &= FD_CLOEXEC;
                        else
                                cloexec = 0;

                        INTOFF;
                        if (big_sh_fd < 10)
                                find_big_fd();
                        if ((bigfd = big_sh_fd) < max_user_fd)
                                bigfd = max_user_fd;
                        if ((i = fcntl(fd, F_DUPFD,
                            (fcntl_int)(bigfd + 1))) == -1) {
                                switch (errno) {
                                case EBADF:
                                        i = CLOSED;
                                        break;
                                case EMFILE:
                                case EINVAL:
                                        find_big_fd();
                                        i = fcntl(fd, F_DUPFD, 
                                                  (fcntl_int) big_sh_fd);
                                        if (i >= 0)
                                                break;
                                        if (errno == EMFILE || errno == EINVAL)
                                                i = fcntl(fd, F_DUPFD,
                                                          (fcntl_int) 3);
                                        if (i >= 0)
                                                break;
                                        /* FALLTHRU */
                                default:
                                        error("%d: %s", fd, strerror(errno));
                                        /* NOTREACHED */
                                }
                        }
                        if (i > biggest_sh_fd)
                                biggest_sh_fd = i;
                        if (i >= 0)
                                (void)fcntl(i, F_SETFD, (fcntl_int) FD_CLOEXEC);
                        fd_rename(sv, fd, i, cloexec);
                        VTRACE(DBG_REDIR, ("fd %d saved as %d%s ", fd, i,
                            cloexec ? "+" : ""));
                        INTON;
                }
                VTRACE(DBG_REDIR, ("%s\n", fd == 0 ? "STDIN" : ""));
                if (fd == 0)
                        fd0_redirected++;
                openredirect(n, memory, flags);
        }
        if (memory[1])
                out1 = &memout;
        if (memory[2])
                out2 = &memout;
}


STATIC void
openredirect(union node *redir, char memory[10], int flags)
{
        struct stat sb;
        int fd = redir->nfile.fd;
        char *fname;
        int f;
        int eflags, cloexec;

        /*
         * We suppress interrupts so that we won't leave open file
         * descriptors around.  This may not be such a good idea because
         * an open of a device or a fifo can block indefinitely.
         */
        INTOFF;
        if (fd < 10)
                memory[fd] = 0;
        switch (redir->nfile.type) {
        case NFROM:
                fname = redir->nfile.expfname;
                if (flags & REDIR_VFORK)
                        eflags = O_NONBLOCK;
                else
                        eflags = 0;
                if ((f = open(fname, O_RDONLY|eflags)) < 0)
                        goto eopen;
                VTRACE(DBG_REDIR, ("openredirect(< '%s') -> %d [%#x]",
                    fname, f, eflags));
                if (eflags)
                        (void)fcntl(f, F_SETFL,
                                  (fcntl_int)(fcntl(f, F_GETFL) & ~eflags));
                break;
        case NFROMTO:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
                        goto ecreate;
                VTRACE(DBG_REDIR, ("openredirect(<> '%s') -> %d", fname, f));
                break;
        case NTO:
                if (Cflag) {
                        fname = redir->nfile.expfname;
                        if ((f = open(fname, O_WRONLY)) == -1) {
                                if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL,
                                    0666)) < 0)
                                        goto ecreate;
                        } else if (fstat(f, &sb) == -1) {
                                int serrno = errno;
                                close(f);
                                errno = serrno;
                                goto ecreate;
                        } else if (S_ISREG(sb.st_mode)) {
                                close(f);
                                errno = EEXIST;
                                goto ecreate;
                        }
                        VTRACE(DBG_REDIR, ("openredirect(>| '%s') -> %d",
                            fname, f));
                        break;
                }
                /* FALLTHROUGH */
        case NCLOBBER:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
                        goto ecreate;
                VTRACE(DBG_REDIR, ("openredirect(> '%s') -> %d", fname, f));
                break;
        case NAPPEND:
                fname = redir->nfile.expfname;
                if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
                        goto ecreate;
                VTRACE(DBG_REDIR, ("openredirect(>> '%s') -> %d", fname, f));
                break;
        case NTOFD:
        case NFROMFD:
                if (redir->ndup.dupfd >= 0) {   /* if not ">&-" */
                        if (sh_fd(redir->ndup.dupfd) != NULL ||
                            saved_redirected_fd(redir->ndup.dupfd) != NULL)
                                error("Redirect (from %d to %d) failed: %s",
                                    redir->ndup.dupfd, fd, strerror(EBADF));
                        if (fd < 10 && redir->ndup.dupfd < 10 &&
                            memory[redir->ndup.dupfd])
                                memory[fd] = 1;
                        else if (copyfd(redir->ndup.dupfd, fd,
                            (flags & REDIR_KEEP) == 0, 0) < 0)
                                error("Redirect (from %d to %d) failed: %s",
                                    redir->ndup.dupfd, fd, strerror(errno));
                        VTRACE(DBG_REDIR, ("openredirect: %d%c&%d\n", fd,
                            "<>"[redir->nfile.type==NTOFD], redir->ndup.dupfd));
                } else {
                        (void) close(fd);
                        VTRACE(DBG_REDIR, ("openredirect: %d%c&-\n", fd,
                            "<>"[redir->nfile.type==NTOFD]));
                }
                INTON;
                return;
        case NHERE:
        case NXHERE:
                VTRACE(DBG_REDIR, ("openredirect: %d<<...", fd));
                f = openhere(redir);
                break;
        default:
                abort();
        }

        if (f > biggest_sh_fd)
                biggest_sh_fd = f;

        cloexec = fd > 2 && (flags & REDIR_KEEP) == 0 && !posix;
        if (f != fd) {
                VTRACE(DBG_REDIR, (" -> %d", fd));
                if (copyfd(f, fd, cloexec, 1) < 0) {
                        int e = errno;

                        VTRACE(DBG_REDIR, (" failed: %s\n", strerror(e)));
                        error("redirect reassignment (fd %d) failed: %s", fd,
                            strerror(e));
                }
        } else if (cloexec)
                (void)fcntl(f, F_SETFD, (fcntl_int) FD_CLOEXEC);
        VTRACE(DBG_REDIR, ("%s\n", cloexec ? " cloexec" : ""));

        INTON;
        return;
 ecreate:
        exerrno = 1;
        error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
 eopen:
        exerrno = 1;
        error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
}


/*
 * Handle here documents.  Normally we fork off a process to write the
 * data to a pipe.  If the document is short, we can stuff the data in
 * the pipe without forking.
 */

STATIC int
openhere(const union node *redir)
{
        int pip[2];
        int len = 0;

        if (pipe(pip) < 0)
                error("Pipe call failed");
        if (pip[1] > biggest_sh_fd)
                biggest_sh_fd = pip[1];
        len = strlen(redir->nhere.text);
        VTRACE(DBG_REDIR, ("openhere(%p) [%d] \"%.*s\"%s\n", redir, len,
            (len < 40 ? len : 40), redir->nhere.text, (len < 40 ? "" : "...")));
        if (len <= PIPESIZE) {          /* XXX eventually copy FreeBSD method */
                xwrite(pip[1], redir->nhere.text, len);
                goto out;
        }
        VTRACE(DBG_REDIR, (" forking [%d,%d]\n", pip[0], pip[1]));
        if (forkshell(NULL, NULL, FORK_NOJOB) == 0) {
                close(pip[0]);
                signal(SIGINT, SIG_IGN);
                signal(SIGQUIT, SIG_IGN);
                signal(SIGHUP, SIG_IGN);
#ifdef SIGTSTP
                signal(SIGTSTP, SIG_IGN);
#endif
                signal(SIGPIPE, SIG_DFL);
                xwrite(pip[1], redir->nhere.text, len);
                VTRACE(DBG_PROCS|DBG_REDIR, ("wrote here doc.  exiting(0)\n"));
                _exit(0);
        }
        VTRACE(DBG_REDIR, ("openhere (closing %d)", pip[1]));
 out:;
        close(pip[1]);
        VTRACE(DBG_REDIR, (" (pipe fd=%d)", pip[0]));
        return pip[0];
}



/*
 * if (reset == POPREDIR_UNDO)
 *      Undo the effects of the last redirection.
 * else if (reset == POPREDIR_PERMANENT)
 *      Make the last redirection permanent
 * else / * reset == POPREDIR_DISCARD * /
 *      Just throw away the redirection
 */

void
popredir(int reset)
{
        struct redirtab *rp = redirlist;

        INTOFF;
        free_rl(rp, reset);
        redirlist = rp->next;
        ckfree(rp);
        INTON;
}

/*
 * Undo all redirections.  Called on error or interrupt.
 */

#ifdef mkinit

INCLUDE "redir.h"

RESET {
        while (redirlist)
                popredir(POPREDIR_UNDO);
}

SHELLPROC {
        clearredir(0);
}

#endif

/* Return true if fd 0 has already been redirected at least once.  */
int
fd0_redirected_p(void)
{
        return fd0_redirected != 0;
}

/*
 * Discard all saved file descriptors.
 */

void
clearredir(int vforked)
{
        struct redirtab *rp;
        struct renamelist *rl;

        /*
         * This happens only in a child process attempting to
         * exec a script which failed ENOEXEC.   Any redirections
         * that have been made are for that script, after it
         * is done, we exit, there is nothing  to restore, so
         * just make the redirections permanent.
         *
         * free_rl() does that does that for us, unless we're
         * a child of a vfork() in which case that is unsafe to
         * call - that should never happen, but just in case, fale
         * it here
         */

        for (rp = redirlist ; rp ; rp = rp->next) {
                if (!vforked)
                        free_rl(rp, POPREDIR_PERMANENT);
                else for (rl = rp->renamed; rl; rl = rl->next)
                        if (rl->into >= 0)
                                close(rl->into);
        }
}



/*
 * Copy a file descriptor (from) to (also) be 'to'..
 * cloexec indicates if we want close-on-exec or not.
 * move indicates if "from" should be closed on success (yes if set).
 * Returns -1 if any error occurs.
 */

STATIC int
copyfd(int from, int to, int cloexec, int move)
{
        int newfd;

        if (cloexec && to > 2) {
#ifdef O_CLOEXEC
                newfd = dup3(from, to, O_CLOEXEC);
#else
                newfd = dup2(from, to);
                if (newfd >= 0)
                        fcntl(newfd, F_SETFD,
                            (fcntl_int)(fcntl(newfd, F_GETFD) | FD_CLOEXEC));
#endif
        } else
                newfd = dup2(from, to);

        if (move && newfd == to && from != to)
                close(from);

        if (newfd != to) {
                if (newfd < 0)
                        error("Unable to dup(%d->%d): %s", from, to,
                            strerror(errno));
                else {
                        close(newfd);
                        error("Moving fd %d to %d made %d!", from, to, newfd);
                }
        }

        if (newfd > biggest_sh_fd)
                biggest_sh_fd = newfd;

        return newfd;
}

/*
 * rename fd from to be fd to (closing from).
 * close-on-exec is never set on 'to' (unless
 * from==to and it was set on from) - ie: a no-op
 * returns to (or errors() if an error occurs).
 *
 * This is mostly used for rearranging the
 * results from pipe().
 */
int
movefd(int from, int to)
{
        if (from > biggest_sh_fd)
                biggest_sh_fd = from;
        if (to > biggest_sh_fd)
                biggest_sh_fd = to;

        if (from == to)
                return to;

        (void)close(to);
        if (copyfd(from, to, 0, 1) != to) {
                int e = errno;

                (void) close(from);
                error("Unable to make fd %d: %s", to, strerror(e));
        }

        return to;
}

STATIC void
find_big_fd(void)
{
        int i, fd;
        static int last_start = 3; /* aim to keep sh fd's under 20 */

        if (last_start < 10)
                last_start++;

        for (i = (1 << last_start); i >= 10; i >>= 1) {
                if ((fd = fcntl(0, F_DUPFD, (fcntl_int)(i - 1))) >= 0) {
                        if (fd > biggest_sh_fd)
                                biggest_sh_fd = fd;
                        close(fd);
                        break;
                }
        }

        fd = (i / 5) * 4;
        if (fd < 10)
                fd = 10;

        big_sh_fd = fd;
}

/*
 * If possible, move file descriptor fd out of the way
 * of expected user fd values.   Returns the new fd
 * (which may be the input fd if things do not go well.)
 * Always set close-on-exec on the result, and close
 * the input fd unless it is to be our result.
 */
int
to_upper_fd(int fd)
{
        int i;

        VTRACE(DBG_REDIR|DBG_OUTPUT, ("to_upper_fd(%d)", fd));
        if (big_sh_fd < 10 || big_sh_fd >= user_fd_limit)
                find_big_fd();
        do {
                i = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int) big_sh_fd);
                if (i >= 0) {
                        if (i > biggest_sh_fd)
                                biggest_sh_fd = i;
                        if (fd != i)
                                close(fd);
                        VTRACE(DBG_REDIR|DBG_OUTPUT, ("-> %d\n", i));
                        return i;
                }
                if (errno != EMFILE && errno != EINVAL)
                        break;
                find_big_fd();
        } while (big_sh_fd > 10);

        /*
         * If we wanted to move this fd to some random high number
         * we certainly do not intend to pass it through exec, even
         * if the reassignment failed.
         */
        (void)fcntl(fd, F_SETFD, (fcntl_int) FD_CLOEXEC);
        VTRACE(DBG_REDIR|DBG_OUTPUT, (" fails ->%d\n", fd));
        return fd;
}

void
register_sh_fd(int fd, void (*cb)(int, int))
{
        struct shell_fds *fp;

        fp = ckmalloc(sizeof (struct shell_fds));
        if (fp != NULL) {
                fp->nxt = sh_fd_list;
                sh_fd_list = fp;

                fp->fd = fd;
                fp->cb = cb;
        }
}

void
sh_close(int fd)
{
        struct shell_fds **fpp, *fp;

        fpp = &sh_fd_list;
        while ((fp = *fpp) != NULL) {
                if (fp->fd == fd) {
                        *fpp = fp->nxt;
                        ckfree(fp);
                        break;
                }
                fpp = &fp->nxt;
        }
        (void)close(fd);
}

STATIC struct shell_fds *
sh_fd(int fd)
{
        struct shell_fds *fp;

        for (fp = sh_fd_list; fp != NULL; fp = fp->nxt)
                if (fp->fd == fd)
                        return fp;
        return NULL;
}

STATIC int
pick_new_fd(int fd)
{
        int to;

        to = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int) big_sh_fd);
        if (to == -1 && big_sh_fd >= 22)
                to = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int) (big_sh_fd / 2));
        if (to == -1)
                to = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int) (fd + 1));
        if (to == -1)
                to = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int) 10);
        if (to == -1)
                to = fcntl(fd, F_DUPFD_CLOEXEC, (fcntl_int)  3);
        if (to == -1)
                error("insufficient file descriptors available");
        CLOEXEC(to);
        if (to > biggest_sh_fd)
                biggest_sh_fd = to;
        return to;
}

STATIC void
renumber_sh_fd(struct shell_fds *fp)
{
        int to;

        if (fp == NULL)
                return;

        /*
         * if we have had a collision, and the sh fd was a "big" one
         * try moving the sh fd base to a higher number (if possible)
         * so future sh fds are less likely to be in the user's sights
         * (incl this one when moved)
         */
        if (fp->fd >= big_sh_fd)
                find_big_fd();

        to = pick_new_fd(fp->fd);

        if (fp->fd == to)       /* impossible? */
                return;

        VTRACE(DBG_REDIR, ("renumber_sh_fd: moved shell fd %d to %d\n",
            fp->fd, to));

        (*fp->cb)(fp->fd, to);
        (void)close(fp->fd);
        fp->fd = to;
}

static const struct flgnames {
        const char *name;
        uint16_t minch;
        uint32_t value;
} nv[] = {
#ifdef O_APPEND
        { "append",     2,      O_APPEND        },
#else
# define O_APPEND 0
#endif
#ifdef O_ASYNC
        { "async",      2,      O_ASYNC         },
#else
# define O_ASYNC 0
#endif
#ifdef O_SYNC
        { "sync",       2,      O_SYNC          },
#else
# define O_SYNC 0
#endif
#ifdef O_NONBLOCK
        { "nonblock",   3,      O_NONBLOCK      },
#else
# define O_NONBLOCK 0
#endif
#ifdef O_FSYNC
        { "fsync",      2,      O_FSYNC         },
#else
# define O_FSYNC 0
#endif
#ifdef O_DSYNC
        { "dsync",      2,      O_DSYNC         },
#else
# define O_DSYNC 0
#endif
#ifdef O_RSYNC
        { "rsync",      2,      O_RSYNC         },
#else
# define O_RSYNC 0
#endif
#ifdef O_ALT_IO
        { "altio",      2,      O_ALT_IO        },
#else
# define O_ALT_IO 0
#endif
#ifdef O_DIRECT
        { "direct",     2,      O_DIRECT        },
#else
# define O_DIRECT 0
#endif
#ifdef O_NOSIGPIPE
        { "nosigpipe",  3,      O_NOSIGPIPE     },
#else
# define O_NOSIGPIPE 0
#endif

#define ALLFLAGS (O_APPEND|O_ASYNC|O_SYNC|O_NONBLOCK|O_DSYNC|O_RSYNC|\
    O_ALT_IO|O_DIRECT|O_NOSIGPIPE)

#ifndef O_CLOEXEC
# define O_CLOEXEC      ((~ALLFLAGS) ^ ((~ALLFLAGS) & ((~ALLFLAGS) - 1)))
#endif

        /* for any system we support, close on exec is always defined */
        { "cloexec",    2,      O_CLOEXEC       },
        { 0, 0, 0 }
};

#ifndef O_ACCMODE
# define O_ACCMODE      0
#endif
#ifndef O_RDONLY
# define O_RDONLY       0
#endif
#ifndef O_WRONLY
# define O_WRONLY       0
#endif
#ifndef O_RWDR
# define O_RWDR         0
#endif
#ifndef O_SHLOCK
# define O_SHLOCK       0
#endif
#ifndef O_EXLOCK
# define O_EXLOCK       0
#endif
#ifndef O_NOFOLLOW
# define O_NOFOLLOW     0
#endif
#ifndef O_CREAT
# define O_CREAT        0
#endif
#ifndef O_TRUNC
# define O_TRUNC        0
#endif
#ifndef O_EXCL
# define O_EXCL         0
#endif
#ifndef O_NOCTTY
# define O_NOCTTY       0
#endif
#ifndef O_DIRECTORY
# define O_DIRECTORY    0
#endif
#ifndef O_REGULAR
# define O_REGULAR      0
#endif
/*
 * flags that F_GETFL might return that we want to ignore
 *
 * F_GETFL should not actually return these, they're all just open()
 * modifiers, rather than state, but just in case...
 */
#define IGNFLAGS (O_ACCMODE|O_RDONLY|O_WRONLY|O_RDWR|O_SHLOCK|O_EXLOCK| \
    O_NOFOLLOW|O_CREAT|O_TRUNC|O_EXCL|O_NOCTTY|O_DIRECTORY|O_REGULAR)

static int
getflags(int fd, int p, int all)
{
        int c, f;

        if (!all && (sh_fd(fd) != NULL || saved_redirected_fd(fd) != NULL)) {
                if (!p)
                        return -1;
                error("Can't get status for fd=%d (%s)", fd, strerror(EBADF));
        }

        if ((c = fcntl(fd, F_GETFD)) == -1) {
                if (!p)
                        return -1;
                error("Can't get status for fd=%d (%s)", fd, strerror(errno));
        }
        if ((f = fcntl(fd, F_GETFL)) == -1) {
                if (!p)
                        return -1;
                error("Can't get flags for fd=%d (%s)", fd, strerror(errno));
        }
        f &= ~IGNFLAGS;         /* clear anything we know about, but ignore */
        if (c & FD_CLOEXEC)
                f |= O_CLOEXEC;
        return f;
}

static void
printone(int fd, int p, int verbose, int pfd)
{
        int f = getflags(fd, p, verbose > 1);
        const struct flgnames *fn;

        if (f == -1)
                return;

        if (pfd)
                outfmt(out1, "%d: ", fd);
        for (fn = nv; fn->name; fn++) {
                if (f & fn->value) {
                        outfmt(out1, "%s%s", verbose ? "+" : "", fn->name);
                        f &= ~fn->value;
                } else if (verbose)
                        outfmt(out1, "-%s", fn->name);
                else
                        continue;
                if (f || (verbose && fn[1].name))
                        outfmt(out1, ",");
        }
        if (verbose && f)               /* f should be normally be 0 */
                outfmt(out1, " +%#x", f);
        outfmt(out1, "\n");
}

static void
parseflags(char *s, int *p, int *n)
{
        int *v, *w;
        const struct flgnames *fn;
        size_t len;

        *p = 0;
        *n = 0;
        for (s = strtok(s, ","); s; s = strtok(NULL, ",")) {
                switch (*s++) {
                case '+':
                        v = p;
                        w = n;
                        break;
                case '-':
                        v = n;
                        w = p;
                        break;
                default:
                        error("Missing +/- indicator before flag %s", s-1);
                }

                len = strlen(s);
                for (fn = nv; fn->name; fn++)
                        if (len >= fn->minch && strncmp(s,fn->name,len) == 0) {
                                *v |= fn->value;
                                *w &=~ fn->value;
                                break;
                        }
                if (fn->name == 0)
                        error("Bad flag `%s'", s);
        }
}

static void
setone(int fd, int pos, int neg, int verbose)
{
        int f = getflags(fd, 1, 0);
        int n, cloexec;

        if (f == -1)
                return;

        cloexec = -1;
        if ((pos & O_CLOEXEC) && !(f & O_CLOEXEC))
                cloexec = FD_CLOEXEC;
        if ((neg & O_CLOEXEC) && (f & O_CLOEXEC))
                cloexec = 0;

        /* Don't allow O_CLOEXEC on stdin, stdout, or stderr */
        if ((cloexec > 0 && fd <= 2 && (errno = EINVAL)) ||
            (cloexec != -1 && fcntl(fd, F_SETFD, (fcntl_int) cloexec) == -1))
                error("Can't set status for fd=%d (%s)", fd, strerror(errno));

        pos &= ~O_CLOEXEC;
        neg &= ~O_CLOEXEC;
        f &= ~O_CLOEXEC;
        n = f;
        n |= pos;
        n &= ~neg;
        if (n != f && fcntl(fd, F_SETFL, (fcntl_int)n) == -1)
                error("Can't set flags for fd=%d (%s)", fd, strerror(errno));
        if (verbose)
                printone(fd, 1, verbose, 1);
}

int
fdflagscmd(int argc, char *argv[])
{
        char *num;
        int verbose = 0, ch, pos = 0, neg = 0;
        char *setflags = NULL;

        optreset = 1; optind = 1; /* initialize getopt */
        while ((ch = getopt(argc, argv, ":vs:"
#ifdef DEBUG
                                             "V"
#endif
                                                )) != -1)
                switch ((char)ch) {
#ifdef DEBUG
                case 'V':
                        verbose = 2;
                        break;
#endif
                case 'v':
                        verbose = 1;
                        break;
                case 's':
                        if (setflags)
                                goto msg;
                        setflags = optarg;
                        break;
                case '?':
                default:
                msg:
                        error("Usage: fdflags [-v] [-s <flags> fd] [fd...]");
                        /* NOTREACHED */
                }

        argc -= optind, argv += optind;

        if (setflags)
                parseflags(setflags, &pos, &neg);

        if (argc == 0) {
                int i;

                if (setflags)
                        goto msg;

                for (i = 0; i <= max_user_fd; i++)
                        printone(i, 0, verbose, 1);
                if (verbose > 1)
                        while (i <= biggest_sh_fd)
                                printone(i++, 0, verbose, 1);

        } else while ((num = *argv++) != NULL) {
                int fd = number(num);

                while (num[0] == '0' && num[1] != '\0')         /* skip 0's */
                        num++;
                if (strlen(num) > 5 ||
                    (fd >= user_fd_limit && fd > max_user_fd))
                        error("%s: too big to be a file descriptor", num);

                if (setflags)
                        setone(fd, pos, neg, verbose);
                else
                        printone(fd, 1, verbose, argc > 1);
        }
        flushout(out1);
        if (io_err(out1)) {
                out2str("fdflags: I/O error\n");
                return 1;
        }
        return 0;
}

#undef MAX              /* in case we inherited them from somewhere */
#undef MIN

#define MIN(a,b)        (/*CONSTCOND*/((a)<=(b)) ? (a) : (b))
#define MAX(a,b)        (/*CONSTCOND*/((a)>=(b)) ? (a) : (b))

                /* now make the compiler work for us... */
#define MIN_REDIR       MIN(MIN(MIN(MIN(NTO,NFROM), MIN(NTOFD,NFROMFD)), \
                   MIN(MIN(NCLOBBER,NAPPEND), MIN(NHERE,NXHERE))), NFROMTO)
#define MAX_REDIR       MAX(MAX(MAX(MAX(NTO,NFROM), MAX(NTOFD,NFROMFD)), \
                   MAX(MAX(NCLOBBER,NAPPEND), MAX(NHERE,NXHERE))), NFROMTO)

static const char *redir_sym[MAX_REDIR - MIN_REDIR + 1] = {
        [NTO      - MIN_REDIR]= ">",
        [NFROM    - MIN_REDIR]= "<",
        [NTOFD    - MIN_REDIR]= ">&",
        [NFROMFD  - MIN_REDIR]= "<&",
        [NCLOBBER - MIN_REDIR]= ">|",
        [NAPPEND  - MIN_REDIR]= ">>",
        [NHERE    - MIN_REDIR]= "<<",
        [NXHERE   - MIN_REDIR]= "<<",
        [NFROMTO  - MIN_REDIR]= "<>",
};

int
outredir(struct output *out, union node *n, int sep)
{
        if (n == NULL)
                return 0;
        if (n->type < MIN_REDIR || n->type > MAX_REDIR ||
            redir_sym[n->type - MIN_REDIR] == NULL)
                return 0;

        if (sep)
                outc(sep, out);

        /*
         * ugly, but all redir node types have "fd" in same slot...
         *      (and code other places assumes it as well)
         */
        if ((redir_sym[n->type - MIN_REDIR][0] == '<' && n->nfile.fd != 0) ||
            (redir_sym[n->type - MIN_REDIR][0] == '>' && n->nfile.fd != 1))
                outfmt(out, "%d", n->nfile.fd);

        outstr(redir_sym[n->type - MIN_REDIR], out);

        switch (n->type) {
        case NHERE:
                outstr("'...'", out);
                break;
        case NXHERE:
                outstr("...", out);
                break;
        case NTOFD:
        case NFROMFD:
                if (n->ndup.dupfd < 0)
                        outc('-', out);
                else
                        outfmt(out, "%d", n->ndup.dupfd);
                break;
        default:
                outstr(n->nfile.expfname, out);
                break;
        }
        return 1;
}