lib/libc/gen/popen.c

   1 /*      $NetBSD: popen.c,v 1.30 2010/11/14 18:11:42 tron 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 1.30 2010/11/14 18:11:42 tron 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
  58 #include "env.h"
  59 #include "reentrant.h"
  60
  61 #ifdef __weak_alias
  62 __weak_alias(popen,_popen)
  63 __weak_alias(pclose,_pclose)
  64 #endif
  65
  66 static struct pid {
  67         struct pid *next;
  68         FILE *fp;
  69 #ifdef _REENTRANT
  70         int fd;
  71 #endif
  72         pid_t pid;
  73 } *pidlist;
  74
  75 #ifdef _REENTRANT
  76 static rwlock_t pidlist_lock = RWLOCK_INITIALIZER;
  77 #endif
  78
  79 FILE *
  80 popen(const char *command, const char *type)
  81 {
  82         struct pid *cur, *old;
  83         FILE *iop;
  84         const char * volatile xtype = type;
  85         int pdes[2], pid, serrno;
  86         volatile int twoway;
  87
  88         _DIAGASSERT(command != NULL);
  89         _DIAGASSERT(xtype != NULL);
  90
  91         if (strchr(xtype, '+')) {
  92                 twoway = 1;
  93                 type = "r+";
  94                 if (socketpair(AF_LOCAL, SOCK_STREAM, 0, pdes) < 0)
  95                         return (NULL);
  96         } else  {
  97                 twoway = 0;
  98                 if ((*xtype != 'r' && *xtype != 'w') || xtype[1] ||
  99                     (pipe(pdes) < 0)) {
 100                         errno = EINVAL;
 101                         return (NULL);
 102                 }
 103         }
 104
 105         if ((cur = malloc(sizeof(struct pid))) == NULL) {
 106                 (void)close(pdes[0]);
 107                 (void)close(pdes[1]);
 108                 errno = ENOMEM;
 109                 return (NULL);
 110         }
 111
 112         (void)rwlock_rdlock(&pidlist_lock);
 113         (void)__readlockenv();
 114         switch (pid = vfork()) {
 115         case -1:                        /* Error. */
 116                 serrno = errno;
 117                 (void)__unlockenv();
 118                 (void)rwlock_unlock(&pidlist_lock);
 119                 free(cur);
 120                 (void)close(pdes[0]);
 121                 (void)close(pdes[1]);
 122                 errno = serrno;
 123                 return (NULL);
 124                 /* NOTREACHED */
 125         case 0:                         /* Child. */
 126                 /* POSIX.2 B.3.2.2 "popen() shall ensure that any streams
 127                    from previous popen() calls that remain open in the
 128                    parent process are closed in the new child process. */
 129                 for (old = pidlist; old; old = old->next)
 130 #ifdef _REENTRANT
 131                         close(old->fd); /* don't allow a flush */
 132 #else
 133                         close(fileno(old->fp)); /* don't allow a flush */
 134 #endif
 135
 136                 if (*xtype == 'r') {
 137                         (void)close(pdes[0]);
 138                         if (pdes[1] != STDOUT_FILENO) {
 139                                 (void)dup2(pdes[1], STDOUT_FILENO);
 140                                 (void)close(pdes[1]);
 141                         }
 142                         if (twoway)
 143                                 (void)dup2(STDOUT_FILENO, STDIN_FILENO);
 144                 } else {
 145                         (void)close(pdes[1]);
 146                         if (pdes[0] != STDIN_FILENO) {
 147                                 (void)dup2(pdes[0], STDIN_FILENO);
 148                                 (void)close(pdes[0]);
 149                         }
 150                 }
 151
 152                 execl(_PATH_BSHELL, "sh", "-c", command, NULL);
 153                 _exit(127);
 154                 /* NOTREACHED */
 155         }
 156         (void)__unlockenv();
 157
 158         /* Parent; assume fdopen can't fail. */
 159         if (*xtype == 'r') {
 160                 iop = fdopen(pdes[0], xtype);
 161 #ifdef _REENTRANT
 162                 cur->fd = pdes[0];
 163 #endif
 164                 (void)close(pdes[1]);
 165         } else {
 166                 iop = fdopen(pdes[1], xtype);
 167 #ifdef _REENTRANT
 168                 cur->fd = pdes[1];
 169 #endif
 170                 (void)close(pdes[0]);
 171         }
 172
 173         /* Link into list of file descriptors. */
 174         cur->fp = iop;
 175         cur->pid =  pid;
 176         cur->next = pidlist;
 177         pidlist = cur;
 178         (void)rwlock_unlock(&pidlist_lock);
 179
 180         return (iop);
 181 }
 182
 183 /*
 184  * pclose --
 185  *      Pclose returns -1 if stream is not associated with a `popened' command,
 186  *      if already `pclosed', or waitpid returns an error.
 187  */
 188 int
 189 pclose(iop)
 190         FILE *iop;
 191 {
 192         struct pid *cur, *last;
 193         int pstat;
 194         pid_t pid;
 195
 196         _DIAGASSERT(iop != NULL);
 197
 198         rwlock_wrlock(&pidlist_lock);
 199
 200         /* Find the appropriate file pointer. */
 201         for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
 202                 if (cur->fp == iop)
 203                         break;
 204         if (cur == NULL) {
 205                 (void)rwlock_unlock(&pidlist_lock);
 206                 return (-1);
 207         }
 208
 209         (void)fclose(iop);
 210
 211         /* Remove the entry from the linked list. */
 212         if (last == NULL)
 213                 pidlist = cur->next;
 214         else
 215                 last->next = cur->next;
 216
 217         (void)rwlock_unlock(&pidlist_lock);
 218
 219         do {
 220                 pid = waitpid(cur->pid, &pstat, 0);
 221         } while (pid == -1 && errno == EINTR);
 222
 223         free(cur);
 224
 225         return (pid == -1 ? -1 : pstat);
 226 }