lib/libc/gen/popen.c

   1 /*      $NetBSD: popen.c,v 1.28 2003/09/15 22:30:38 cl Exp $    */
   2
   3 /*
   4  * Copyright (c) 1988, 1993
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software written by Ken Arnold and
   8  * published in UNIX Review, Vol. 6, No. 8.
   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 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)popen.c     8.3 (Berkeley) 5/3/95";
  39 #else
  40 __RCSID("$NetBSD: popen.c,v 1.28 2003/09/15 22:30:38 cl Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #include "namespace.h"
  45 #include <sys/param.h>
  46 #include <sys/wait.h>
  47 #include <sys/socket.h>
  48
  49 #include <assert.h>
  50 #include <errno.h>
  51 #include <paths.h>
  52 #include <signal.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57 #include "reentrant.h"
  58
  59 #ifdef __weak_alias
  60 __weak_alias(popen,_popen)
  61 __weak_alias(pclose,_pclose)
  62 #endif
  63
  64 #ifdef _REENTRANT
  65 extern rwlock_t __environ_lock;
  66 #endif
  67
  68 static struct pid {
  69         struct pid *next;
  70         FILE *fp;
  71 #ifdef _REENTRANT
  72         int fd;
  73 #endif
  74         pid_t pid;
  75 } *pidlist;
  76
  77 #ifdef _REENTRANT
  78 static rwlock_t pidlist_lock = RWLOCK_INITIALIZER;
  79 #endif
  80
  81 FILE *
  82 popen(const char *command, const char *type)
  83 {
  84         struct pid *cur, *old;
  85         FILE *iop;
  86         const char * volatile xtype = type;
  87         int pdes[2], pid, serrno;
  88         volatile int twoway;
  89
  90         _DIAGASSERT(command != NULL);
  91         _DIAGASSERT(xtype != NULL);
  92
  93         if (strchr(xtype, '+')) {
  94                 twoway = 1;
  95                 type = "r+";
  96                 if (socketpair(AF_LOCAL, SOCK_STREAM, 0, pdes) < 0)
  97                         return (NULL);
  98         } else  {
  99                 twoway = 0;
 100                 if ((*xtype != 'r' && *xtype != 'w') || xtype[1] ||
 101                     (pipe(pdes) < 0)) {
 102                         errno = EINVAL;
 103                         return (NULL);
 104                 }
 105         }
 106
 107         if ((cur = malloc(sizeof(struct pid))) == NULL) {
 108                 (void)close(pdes[0]);
 109                 (void)close(pdes[1]);
 110                 errno = ENOMEM;
 111                 return (NULL);
 112         }
 113
 114         rwlock_rdlock(&pidlist_lock);
 115         rwlock_rdlock(&__environ_lock);
 116         switch (pid = vfork()) {
 117         case -1:                        /* Error. */
 118                 serrno = errno;
 119                 rwlock_unlock(&__environ_lock);
 120                 rwlock_unlock(&pidlist_lock);
 121                 free(cur);
 122                 (void)close(pdes[0]);
 123                 (void)close(pdes[1]);
 124                 errno = serrno;
 125                 return (NULL);
 126                 /* NOTREACHED */
 127         case 0:                         /* Child. */
 128                 /* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
 129                    from previous popen() calls that remain open in the
 130                    parent process are closed in the new child process. */
 131                 for (old = pidlist; old; old = old->next)
 132 #ifdef _REENTRANT
 133                         close(old->fd); /* don't allow a flush */
 134 #else
 135                         close(fileno(old->fp)); /* don't allow a flush */
 136 #endif
 137
 138                 if (*xtype == 'r') {
 139                         (void)close(pdes[0]);
 140                         if (pdes[1] != STDOUT_FILENO) {
 141                                 (void)dup2(pdes[1], STDOUT_FILENO);
 142                                 (void)close(pdes[1]);
 143                         }
 144                         if (twoway)
 145                                 (void)dup2(STDOUT_FILENO, STDIN_FILENO);
 146                 } else {
 147                         (void)close(pdes[1]);
 148                         if (pdes[0] != STDIN_FILENO) {
 149                                 (void)dup2(pdes[0], STDIN_FILENO);
 150                                 (void)close(pdes[0]);
 151                         }
 152                 }
 153
 154                 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
 155                 _exit(127);
 156                 /* NOTREACHED */
 157         }
 158         rwlock_unlock(&__environ_lock);
 159
 160         /* Parent; assume fdopen can't fail. */
 161         if (*xtype == 'r') {
 162                 iop = fdopen(pdes[0], xtype);
 163 #ifdef _REENTRANT
 164                 cur->fd = pdes[0];
 165 #endif
 166                 (void)close(pdes[1]);
 167         } else {
 168                 iop = fdopen(pdes[1], xtype);
 169 #ifdef _REENTRANT
 170                 cur->fd = pdes[1];
 171 #endif
 172                 (void)close(pdes[0]);
 173         }
 174
 175         /* Link into list of file descriptors. */
 176         cur->fp = iop;
 177         cur->pid =  pid;
 178         cur->next = pidlist;
 179         pidlist = cur;
 180         rwlock_unlock(&pidlist_lock);
 181
 182         return (iop);
 183 }
 184
 185 /*
 186  * pclose --
 187  *      Pclose returns -1 if stream is not associated with a `popened' command,
 188  *      if already `pclosed', or waitpid returns an error.
 189  */
 190 int
 191 pclose(iop)
 192         FILE *iop;
 193 {
 194         struct pid *cur, *last;
 195         int pstat;
 196         pid_t pid;
 197
 198         _DIAGASSERT(iop != NULL);
 199
 200         rwlock_wrlock(&pidlist_lock);
 201
 202         /* Find the appropriate file pointer. */
 203         for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
 204                 if (cur->fp == iop)
 205                         break;
 206         if (cur == NULL) {
 207                 rwlock_unlock(&pidlist_lock);
 208                 return (-1);
 209         }
 210
 211         (void)fclose(iop);
 212
 213         /* Remove the entry from the linked list. */
 214         if (last == NULL)
 215                 pidlist = cur->next;
 216         else
 217                 last->next = cur->next;
 218
 219         rwlock_unlock(&pidlist_lock);
 220
 221         do {
 222                 pid = waitpid(cur->pid, &pstat, 0);
 223         } while (pid == -1 && errno == EINTR);
 224
 225         free(cur);
 226
 227         return (pid == -1 ? -1 : pstat);
 228 }