lib/libc/gen/popen.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software written by Ken Arnold and
   6  * published in UNIX Review, Vol. 6, No. 8.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)popen.c  8.3 (Berkeley) 5/3/95
  33  * $FreeBSD: src/lib/libc/gen/popen.c,v 1.20 2008/07/29 16:29:59 ed Exp $
  34  * $DragonFly: src/lib/libc/gen/popen.3,v 1.4 2006/04/08 08:17:06 swildner Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <sys/param.h>
  39 #include <sys/queue.h>
  40 #include <sys/wait.h>
  41
  42 #include <signal.h>
  43 #include <errno.h>
  44 #include <unistd.h>
  45 #include <stdio.h>
  46 #include <stdlib.h>
  47 #include <string.h>
  48 #include <paths.h>
  49 #include <pthread.h>
  50 #include "un-namespace.h"
  51 #include "libc_private.h"
  52
  53 extern char **environ;
  54
  55 struct pid {
  56         SLIST_ENTRY(pid) next;
  57         FILE *fp;
  58         pid_t pid;
  59 };
  60 static SLIST_HEAD(, pid) pidlist = SLIST_HEAD_INITIALIZER(pidlist);
  61 static pthread_mutex_t pidlist_mutex = PTHREAD_MUTEX_INITIALIZER;
  62
  63 #define THREAD_LOCK()   if (__isthreaded) _pthread_mutex_lock(&pidlist_mutex)
  64 #define THREAD_UNLOCK() if (__isthreaded) _pthread_mutex_unlock(&pidlist_mutex)
  65
  66 FILE *
  67 popen(const char *command, const char *type)
  68 {
  69         struct pid *cur;
  70         FILE *iop;
  71         int pdes[2], pid, twoway;
  72         const char *argv[4];
  73         struct pid *p;
  74
  75         /*
  76          * Lite2 introduced two-way popen() pipes using _socketpair().
  77          * FreeBSD's pipe() is bidirectional, so we use that.
  78          */
  79         if (strchr(type, '+')) {
  80                 twoway = 1;
  81                 type = "r+";
  82         } else  {
  83                 twoway = 0;
  84                 if ((*type != 'r' && *type != 'w') || type[1])
  85                         return (NULL);
  86         }
  87         if (pipe(pdes) < 0)
  88                 return (NULL);
  89
  90         if ((cur = malloc(sizeof(struct pid))) == NULL) {
  91                 _close(pdes[0]);
  92                 _close(pdes[1]);
  93                 return (NULL);
  94         }
  95
  96         argv[0] = "sh";
  97         argv[1] = "-c";
  98         argv[2] = command;
  99         argv[3] = NULL;
 100
 101         THREAD_LOCK();
 102         switch (pid = vfork()) {
 103         case -1:                        /* Error. */
 104                 THREAD_UNLOCK();
 105                 _close(pdes[0]);
 106                 _close(pdes[1]);
 107                 free(cur);
 108                 return (NULL);
 109                 /* NOTREACHED */
 110         case 0:                         /* Child. */
 111                 if (*type == 'r') {
 112                         /*
 113                          * The _dup2() to STDIN_FILENO is repeated to avoid
 114                          * writing to pdes[1], which might corrupt the
 115                          * parent's copy.  This isn't good enough in
 116                          * general, since the _exit() is no return, so
 117                          * the compiler is free to corrupt all the local
 118                          * variables.
 119                          */
 120                         _close(pdes[0]);
 121                         if (pdes[1] != STDOUT_FILENO) {
 122                                 _dup2(pdes[1], STDOUT_FILENO);
 123                                 _close(pdes[1]);
 124                                 if (twoway)
 125                                         _dup2(STDOUT_FILENO, STDIN_FILENO);
 126                         } else if (twoway && (pdes[1] != STDIN_FILENO))
 127                                 _dup2(pdes[1], STDIN_FILENO);
 128                 } else {
 129                         if (pdes[0] != STDIN_FILENO) {
 130                                 _dup2(pdes[0], STDIN_FILENO);
 131                                 _close(pdes[0]);
 132                         }
 133                         _close(pdes[1]);
 134                 }
 135                 SLIST_FOREACH(p, &pidlist, next)
 136                         _close(fileno(p->fp));
 137                 _execve(_PATH_BSHELL, __DECONST(char * const *, argv), environ);
 138                 _exit(127);
 139                 /* NOTREACHED */
 140         }
 141         THREAD_UNLOCK();
 142
 143         /* Parent; assume fdopen can't fail. */
 144         if (*type == 'r') {
 145                 iop = fdopen(pdes[0], type);
 146                 _close(pdes[1]);
 147         } else {
 148                 iop = fdopen(pdes[1], type);
 149                 _close(pdes[0]);
 150         }
 151
 152         /* Link into list of file descriptors. */
 153         cur->fp = iop;
 154         cur->pid = pid;
 155         THREAD_LOCK();
 156         SLIST_INSERT_HEAD(&pidlist, cur, next);
 157         THREAD_UNLOCK();
 158
 159         return (iop);
 160 }
 161
 162 /*
 163  * pclose --
 164  *      Pclose returns -1 if stream is not associated with a `popened' command,
 165  *      if already `pclosed', or waitpid returns an error.
 166  */
 167 int
 168 pclose(FILE *iop)
 169 {
 170         struct pid *cur, *last = NULL;
 171         int pstat;
 172         pid_t pid;
 173
 174         /*
 175          * Find the appropriate file pointer and remove it from the list.
 176          */
 177         THREAD_LOCK();
 178         SLIST_FOREACH(cur, &pidlist, next) {
 179                 if (cur->fp == iop)
 180                         break;
 181                 last = cur;
 182         }
 183         if (cur == NULL) {
 184                 THREAD_UNLOCK();
 185                 return (-1);
 186         }
 187         if (last == NULL)
 188                 SLIST_REMOVE_HEAD(&pidlist, next);
 189         else
 190                 SLIST_REMOVE_NEXT(&pidlist, last, next);
 191         THREAD_UNLOCK();
 192
 193         fclose(iop);
 194
 195         do {
 196                 pid = _wait4(cur->pid, &pstat, 0, (struct rusage *)0);
 197         } while (pid == -1 && errno == EINTR);
 198
 199         free(cur);
 200
 201         return (pid == -1 ? -1 : pstat);
 202 }