sh/redir.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-3-Clause
   3  *
   4  * Copyright (c) 1991, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Kenneth Almquist.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #ifndef lint
  36 #if 0
  37 static char sccsid[] = "@(#)redir.c     8.2 (Berkeley) 5/4/95";
  38 #endif
  39 #endif /* not lint */
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: head/bin/sh/redir.c 326025 2017-11-20 19:49:47Z pfg $");
  42
  43 #include <sys/types.h>
  44 #include <sys/stat.h>
  45 #include <signal.h>
  46 #include <string.h>
  47 #include <fcntl.h>
  48 #include <errno.h>
  49 #include <unistd.h>
  50 #include <stdlib.h>
  51
  52 /*
  53  * Code for dealing with input/output redirection.
  54  */
  55
  56 #include "shell.h"
  57 #include "nodes.h"
  58 #include "jobs.h"
  59 #include "expand.h"
  60 #include "redir.h"
  61 #include "output.h"
  62 #include "memalloc.h"
  63 #include "error.h"
  64 #include "options.h"
  65
  66
  67 #define EMPTY -2                /* marks an unused slot in redirtab */
  68 #define CLOSED -1               /* fd was not open before redir */
  69
  70
  71 struct redirtab {
  72         struct redirtab *next;
  73         int renamed[10];
  74         int fd0_redirected;
  75         unsigned int empty_redirs;
  76 };
  77
  78
  79 static struct redirtab *redirlist;
  80
  81 /*
  82  * We keep track of whether or not fd0 has been redirected.  This is for
  83  * background commands, where we want to redirect fd0 to /dev/null only
  84  * if it hasn't already been redirected.
  85 */
  86 static int fd0_redirected = 0;
  87
  88 /* Number of redirtabs that have not been allocated. */
  89 static unsigned int empty_redirs = 0;
  90
  91 static void openredirect(union node *, char[10 ]);
  92 static int openhere(union node *);
  93
  94
  95 /*
  96  * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
  97  * old file descriptors are stashed away so that the redirection can be
  98  * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
  99  * standard output, and the standard error if it becomes a duplicate of
 100  * stdout, is saved in memory.
 101 *
 102  * We suppress interrupts so that we won't leave open file
 103  * descriptors around.  Because the signal handler remains
 104  * installed and we do not use system call restart, interrupts
 105  * will still abort blocking opens such as fifos (they will fail
 106  * with EINTR). There is, however, a race condition if an interrupt
 107  * arrives after INTOFF and before open blocks.
 108  */
 109
 110 void
 111 redirect(union node *redir, int flags)
 112 {
 113         union node *n;
 114         struct redirtab *sv = NULL;
 115         int i;
 116         int fd;
 117         char memory[10];        /* file descriptors to write to memory */
 118
 119         INTOFF;
 120         for (i = 10 ; --i >= 0 ; )
 121                 memory[i] = 0;
 122         memory[1] = flags & REDIR_BACKQ;
 123         if (flags & REDIR_PUSH) {
 124                 empty_redirs++;
 125                 if (redir != NULL) {
 126                         sv = ckmalloc(sizeof (struct redirtab));
 127                         for (i = 0 ; i < 10 ; i++)
 128                                 sv->renamed[i] = EMPTY;
 129                         sv->fd0_redirected = fd0_redirected;
 130                         sv->empty_redirs = empty_redirs - 1;
 131                         sv->next = redirlist;
 132                         redirlist = sv;
 133                         empty_redirs = 0;
 134                 }
 135         }
 136         for (n = redir ; n ; n = n->nfile.next) {
 137                 fd = n->nfile.fd;
 138                 if (fd == 0)
 139                         fd0_redirected = 1;
 140                 if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
 141                     n->ndup.dupfd == fd)
 142                         continue; /* redirect from/to same file descriptor */
 143
 144                 if ((flags & REDIR_PUSH) && sv->renamed[fd] == EMPTY) {
 145                         INTOFF;
 146                         if ((i = fcntl(fd, F_DUPFD_CLOEXEC, 10)) == -1) {
 147                                 switch (errno) {
 148                                 case EBADF:
 149                                         i = CLOSED;
 150                                         break;
 151                                 default:
 152                                         INTON;
 153                                         error("%d: %s", fd, strerror(errno));
 154                                         break;
 155                                 }
 156                         }
 157                         sv->renamed[fd] = i;
 158                         INTON;
 159                 }
 160                 openredirect(n, memory);
 161                 INTON;
 162                 INTOFF;
 163         }
 164         if (memory[1])
 165                 out1 = &memout;
 166         if (memory[2])
 167                 out2 = &memout;
 168         INTON;
 169 }
 170
 171
 172 static void
 173 openredirect(union node *redir, char memory[10])
 174 {
 175         struct stat sb;
 176         int fd = redir->nfile.fd;
 177         const char *fname;
 178         int f;
 179         int e;
 180
 181         memory[fd] = 0;
 182         switch (redir->nfile.type) {
 183         case NFROM:
 184                 fname = redir->nfile.expfname;
 185                 if ((f = open(fname, O_RDONLY)) < 0)
 186                         error("cannot open %s: %s", fname, strerror(errno));
 187                 break;
 188         case NFROMTO:
 189                 fname = redir->nfile.expfname;
 190                 if ((f = open(fname, O_RDWR|O_CREAT, 0666)) < 0)
 191                         error("cannot create %s: %s", fname, strerror(errno));
 192                 break;
 193         case NTO:
 194                 if (Cflag) {
 195                         fname = redir->nfile.expfname;
 196                         if (stat(fname, &sb) == -1) {
 197                                 if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL, 0666)) < 0)
 198                                         error("cannot create %s: %s", fname, strerror(errno));
 199                         } else if (!S_ISREG(sb.st_mode)) {
 200                                 if ((f = open(fname, O_WRONLY, 0666)) < 0)
 201                                         error("cannot create %s: %s", fname, strerror(errno));
 202                                 if (fstat(f, &sb) != -1 && S_ISREG(sb.st_mode)) {
 203                                         close(f);
 204                                         error("cannot create %s: %s", fname,
 205                                             strerror(EEXIST));
 206                                 }
 207                         } else
 208                                 error("cannot create %s: %s", fname,
 209                                     strerror(EEXIST));
 210                         break;
 211                 }
 212                 /* FALLTHROUGH */
 213         case NCLOBBER:
 214                 fname = redir->nfile.expfname;
 215                 if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
 216                         error("cannot create %s: %s", fname, strerror(errno));
 217                 break;
 218         case NAPPEND:
 219                 fname = redir->nfile.expfname;
 220                 if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
 221                         error("cannot create %s: %s", fname, strerror(errno));
 222                 break;
 223         case NTOFD:
 224         case NFROMFD:
 225                 if (redir->ndup.dupfd >= 0) {   /* if not ">&-" */
 226                         if (memory[redir->ndup.dupfd])
 227                                 memory[fd] = 1;
 228                         else {
 229                                 if (dup2(redir->ndup.dupfd, fd) < 0)
 230                                         error("%d: %s", redir->ndup.dupfd,
 231                                                         strerror(errno));
 232                         }
 233                 } else {
 234                         close(fd);
 235                 }
 236                 return;
 237         case NHERE:
 238         case NXHERE:
 239                 f = openhere(redir);
 240                 break;
 241         default:
 242                 abort();
 243         }
 244         if (f != fd) {
 245                 if (dup2(f, fd) == -1) {
 246                         e = errno;
 247                         close(f);
 248                         error("%d: %s", fd, strerror(e));
 249                 }
 250                 close(f);
 251         }
 252 }
 253
 254
 255 /*
 256  * Handle here documents.  Normally we fork off a process to write the
 257  * data to a pipe.  If the document is short, we can stuff the data in
 258  * the pipe without forking.
 259  */
 260
 261 static int
 262 openhere(union node *redir)
 263 {
 264         const char *p;
 265         int pip[2];
 266         size_t len = 0;
 267         int flags;
 268         ssize_t written = 0;
 269
 270         if (pipe(pip) < 0)
 271                 error("Pipe call failed: %s", strerror(errno));
 272
 273         if (redir->type == NXHERE)
 274                 p = redir->nhere.expdoc;
 275         else
 276                 p = redir->nhere.doc->narg.text;
 277         len = strlen(p);
 278         if (len == 0)
 279                 goto out;
 280         flags = fcntl(pip[1], F_GETFL, 0);
 281         if (flags != -1 && fcntl(pip[1], F_SETFL, flags | O_NONBLOCK) != -1) {
 282                 written = write(pip[1], p, len);
 283                 if (written < 0)
 284                         written = 0;
 285                 if ((size_t)written == len)
 286                         goto out;
 287                 fcntl(pip[1], F_SETFL, flags);
 288         }
 289
 290         if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
 291                 close(pip[0]);
 292                 signal(SIGINT, SIG_IGN);
 293                 signal(SIGQUIT, SIG_IGN);
 294                 signal(SIGHUP, SIG_IGN);
 295                 signal(SIGTSTP, SIG_IGN);
 296                 signal(SIGPIPE, SIG_DFL);
 297                 xwrite(pip[1], p + written, len - written);
 298                 _exit(0);
 299         }
 300 out:
 301         close(pip[1]);
 302         return pip[0];
 303 }
 304
 305
 306
 307 /*
 308  * Undo the effects of the last redirection.
 309  */
 310
 311 void
 312 popredir(void)
 313 {
 314         struct redirtab *rp = redirlist;
 315         int i;
 316
 317         INTOFF;
 318         if (empty_redirs > 0) {
 319                 empty_redirs--;
 320                 INTON;
 321                 return;
 322         }
 323         for (i = 0 ; i < 10 ; i++) {
 324                 if (rp->renamed[i] != EMPTY) {
 325                         if (rp->renamed[i] >= 0) {
 326                                 dup2(rp->renamed[i], i);
 327                                 close(rp->renamed[i]);
 328                         } else {
 329                                 close(i);
 330                         }
 331                 }
 332         }
 333         fd0_redirected = rp->fd0_redirected;
 334         empty_redirs = rp->empty_redirs;
 335         redirlist = rp->next;
 336         ckfree(rp);
 337         INTON;
 338 }
 339
 340 /* Return true if fd 0 has already been redirected at least once.  */
 341 int
 342 fd0_redirected_p(void)
 343 {
 344         return fd0_redirected != 0;
 345 }
 346
 347 /*
 348  * Discard all saved file descriptors.
 349  */
 350
 351 void
 352 clearredir(void)
 353 {
 354         struct redirtab *rp;
 355         int i;
 356
 357         for (rp = redirlist ; rp ; rp = rp->next) {
 358                 for (i = 0 ; i < 10 ; i++) {
 359                         if (rp->renamed[i] >= 0) {
 360                                 close(rp->renamed[i]);
 361                         }
 362                         rp->renamed[i] = EMPTY;
 363                 }
 364         }
 365 }