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redir.c

/*    $NetBSD: redir.c,v 1.27 2002/11/24 22:35:42 christos 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by the University of
 *    California, Berkeley and its contributors.
 * 4. 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 1.27 2002/11/24 22:35:42 christos Exp $");
#endif
#endif /* not lint */

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

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

#include "main.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 "error.h"


#define EMPTY -2        /* marks an unused slot in redirtab */
#ifndef PIPE_BUF
# define PIPESIZE 4096        /* amount of buffering in a pipe */
#else
# define PIPESIZE PIPE_BUF
#endif


MKINIT
struct redirtab {
      struct redirtab *next;
      int renamed[10];
      int nullredirs;
};


MKINIT struct redirtab *redirlist;
MKINIT int nullredirs;

STATIC int openredirect(union node *);
#ifdef notyet
STATIC void dupredirect(union node *, int, char[10]);
#else
STATIC void dupredirect(union node *, int);
#endif
STATIC int openhere(union node *);
STATIC int noclobberopen(const char *);


/*
 * 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;
      int i;
      int fd;
      int newfd;
      int *p;
#if notyet
      char memory[10];  /* file descriptors to write to memory */

      for (i = 10 ; --i >= 0 ; )
            memory[i] = 0;
      memory[1] = flags & REDIR_BACKQ;
#endif
      nullredirs++;
      if (!redir) {
            return;
      }
      sv = NULL;
      INTOFF;
      if (flags & REDIR_PUSH) {
            struct redirtab *q;
            q = ckmalloc(sizeof (struct redirtab));
            q->next = redirlist;
            redirlist = q;
            q->nullredirs = nullredirs - 1;
            for (i = 0 ; i < 10 ; i++)
                  q->renamed[i] = EMPTY;
            nullredirs = 0;
            sv = q;
      }
      n = redir;
      do {
            fd = n->nfile.fd;
            if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
                n->ndup.dupfd == fd)
                  continue; /* redirect from/to same file descriptor */

            newfd = openredirect(n);
            if (fd == newfd)
                  continue;
            if (sv && *(p = &sv->renamed[fd]) == EMPTY) {
                  int i = fcntl(fd, F_DUPFD, 10);
                  if (i == -1) {
                        i = errno;
                        if (i != EBADF) {
                              const char *m = strerror(i);
                              close(newfd);
                              error("%d: %s", fd, m);
                              /* NOTREACHED */
                        }
                  } else {
                        *p = i;
                        close(fd);
                  }
            } else {
                  close(fd);
            }
#ifdef notyet
            dupredirect(n, newfd, memory);
#else
            dupredirect(n, newfd);
#endif
      } while ((n = n->nfile.next));
      INTON;
#ifdef notyet
      if (memory[1])
            out1 = &memout;
      if (memory[2])
            out2 = &memout;
#endif
      if (flags & REDIR_SAVEFD2 && sv && sv->renamed[2] >= 0)
            preverrout.fd = sv->renamed[2];
}


STATIC int
openredirect(union node *redir)
{
      char *fname;
      int f;

      switch (redir->nfile.type) {
      case NFROM:
            fname = redir->nfile.expfname;
            if ((f = open64(fname, O_RDONLY)) < 0)
                  goto eopen;
            break;
      case NFROMTO:
            fname = redir->nfile.expfname;
            if ((f = open64(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
                  goto ecreate;
            break;
      case NTO:
            /* Take care of noclobber mode. */
            if (Cflag) {
                  fname = redir->nfile.expfname;
                  if ((f = noclobberopen(fname)) < 0)
                        goto ecreate;
                  break;
            }
            /* FALLTHROUGH */
      case NCLOBBER:
            fname = redir->nfile.expfname;
            if ((f = open64(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
                  goto ecreate;
            break;
      case NAPPEND:
            fname = redir->nfile.expfname;
            if ((f = open64(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
                  goto ecreate;
            break;
      default:
#ifdef DEBUG
            abort();
#endif
            /* Fall through to eliminate warning. */
      case NTOFD:
      case NFROMFD:
            f = -1;
            break;
      case NHERE:
      case NXHERE:
            f = openhere(redir);
            break;
      }

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


STATIC void
#ifdef notyet
dupredirect(redir, f, memory)
#else
dupredirect(redir, f)
#endif
      union node *redir;
      int f;
#ifdef notyet
      char memory[10];
#endif
      {
      int fd = redir->nfile.fd;

#ifdef notyet
      memory[fd] = 0;
#endif
      if (redir->nfile.type == NTOFD || redir->nfile.type == NFROMFD) {
            if (redir->ndup.dupfd >= 0) { /* if not ">&-" */
#ifdef notyet
                  if (memory[redir->ndup.dupfd])
                        memory[fd] = 1;
                  else
#endif
                        copyfd(redir->ndup.dupfd, fd);
            }
            return;
      }

      if (f != fd) {
            copyfd(f, fd);
            close(f);
      }
      return;
}


/*
 * 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(union node *redir)
{
      int pip[2];
      size_t len = 0;

      if (pipe(pip) < 0)
            error("Pipe call failed");
      if (redir->type == NHERE) {
            len = strlen(redir->nhere.doc->narg.text);
            if (len <= PIPESIZE) {
                  xwrite(pip[1], redir->nhere.doc->narg.text, len);
                  goto out;
            }
      }
      if (forkshell((struct job *)NULL, (union node *)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);
            if (redir->type == NHERE)
                  xwrite(pip[1], redir->nhere.doc->narg.text, len);
            else
                  expandhere(redir->nhere.doc, pip[1]);
            _exit(0);
      }
out:
      close(pip[1]);
      return pip[0];
}



/*
 * Undo the effects of the last redirection.
 */

void
popredir(int drop)
{
      struct redirtab *rp;
      int i;

      if (--nullredirs >= 0)
            return;
      INTOFF;
      rp = redirlist;
      for (i = 0 ; i < 10 ; i++) {
            if (rp->renamed[i] != EMPTY) {
                  if (!drop) {
                        close(i);
                        copyfd(rp->renamed[i], i);
                  }
                  close(rp->renamed[i]);
            }
      }
      redirlist = rp->next;
      nullredirs = rp->nullredirs;
      ckfree(rp);
      INTON;
}

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

#ifdef mkinit

INCLUDE "redir.h"

RESET {
      clearredir(0);
}

#endif

/*
 * Discard all saved file descriptors.
 */

void
clearredir(int drop)
{
      for (;;) {
            nullredirs = 0;
            if (!redirlist)
                  break;
            popredir(drop);
      }
}



/*
 * Copy a file descriptor to be >= to.  Returns -1
 * if the source file descriptor is closed, EMPTY if there are no unused
 * file descriptors left.
 */

int
copyfd(int from, int to)
{
      int newfd;

      newfd = fcntl(from, F_DUPFD, to);
      if (newfd < 0) {
            int errno2 = errno;
            if (errno2 == EMFILE)
                  return EMPTY;
            else
                  error("%d: %s", from, strerror(errno2));
      }
      return newfd;
}


/*
 * Open a file in noclobber mode.
 * The code was copied from bash.
 */
int
noclobberopen(fname)
      const char *fname;
{
      int r, fd;
      struct stat64 finfo, finfo2;

      /*
       * If the file exists and is a regular file, return an error
       * immediately.
       */
      r = stat64(fname, &finfo);
      if (r == 0 && S_ISREG(finfo.st_mode)) {
            errno = EEXIST;
            return -1;
      }

      /*
       * If the file was not present (r != 0), make sure we open it
       * exclusively so that if it is created before we open it, our open
       * will fail.  Make sure that we do not truncate an existing file.
       * Note that we don't turn on O_EXCL unless the stat failed -- if the
       * file was not a regular file, we leave O_EXCL off.
       */
      if (r != 0)
            return open64(fname, O_WRONLY|O_CREAT|O_EXCL, 0666);
      fd = open64(fname, O_WRONLY|O_CREAT, 0666);

      /* If the open failed, return the file descriptor right away. */
      if (fd < 0)
            return fd;

      /*
       * OK, the open succeeded, but the file may have been changed from a
       * non-regular file to a regular file between the stat and the open.
       * We are assuming that the O_EXCL open handles the case where FILENAME
       * did not exist and is symlinked to an existing file between the stat
       * and open.
       */

      /*
       * If we can open it and fstat the file descriptor, and neither check
       * revealed that it was a regular file, and the file has not been
       * replaced, return the file descriptor.
       */
       if (fstat64(fd, &finfo2) == 0 && !S_ISREG(finfo2.st_mode) &&
           finfo.st_dev == finfo2.st_dev && finfo.st_ino == finfo2.st_ino)
            return fd;

      /* The file has been replaced.  badness. */
      close(fd);
      errno = EEXIST;
      return -1;
}


int
redirectsafe(union node *redir, int flags)
{
      int err;
      volatile int saveint;
      struct jmploc *volatile savehandler = handler;
      struct jmploc jmploc;

      SAVEINT(saveint);
      if (!(err = setjmp(jmploc.loc) * 2)) {
            handler = &jmploc;
            redirect(redir, flags);
      }
      handler = savehandler;
      if (err && exception != EXERROR)
            longjmp(handler->loc, 1);
      RESTOREINT(saveint);
      return err;
}

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