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  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * $FreeBSD: src/lib/libc/gen/popen.c,v 1.14 2000/01/27 23:06:19 jasone Exp $
  37  * $DragonFly: src/lib/libc/gen/popen.c,v 1.6 2005/11/13 00:07:42 swildner Exp $
  38  *
  39  * @(#)popen.c  8.3 (Berkeley) 5/3/95
  40  */
  41
  42 #include "namespace.h"
  43 #include <sys/param.h>
  44 #include <sys/wait.h>
  45
  46 #include <signal.h>
  47 #include <errno.h>
  48 #include <unistd.h>
  49 #include <stdio.h>
  50 #include <stdlib.h>
  51 #include <string.h>
  52 #include <paths.h>
  53 #include "un-namespace.h"
  54
  55 extern char **environ;
  56
  57 static struct pid {
  58         struct pid *next;
  59         FILE *fp;
  60         pid_t pid;
  61 } *pidlist;
  62
  63 FILE *
  64 popen(const char *command, const char *type)
  65 {
  66         struct pid *cur;
  67         FILE *iop;
  68         int pdes[2], pid, twoway;
  69         const char *argv[4];
  70         struct pid *p;
  71
  72         /*
  73          * Lite2 introduced two-way popen() pipes using _socketpair().
  74          * FreeBSD's pipe() is bidirectional, so we use that.
  75          */
  76         if (strchr(type, '+')) {
  77                 twoway = 1;
  78                 type = "r+";
  79         } else  {
  80                 twoway = 0;
  81                 if ((*type != 'r' && *type != 'w') || type[1])
  82                         return (NULL);
  83         }
  84         if (pipe(pdes) < 0)
  85                 return (NULL);
  86
  87         if ((cur = malloc(sizeof(struct pid))) == NULL) {
  88                 _close(pdes[0]);
  89                 _close(pdes[1]);
  90                 return (NULL);
  91         }
  92
  93         argv[0] = "sh";
  94         argv[1] = "-c";
  95         argv[2] = command;
  96         argv[3] = NULL;
  97
  98         switch (pid = fork()) {
  99         case -1:                        /* Error. */
 100                 _close(pdes[0]);
 101                 _close(pdes[1]);
 102                 free(cur);
 103                 return (NULL);
 104                 /* NOTREACHED */
 105         case 0:                         /* Child. */
 106                 if (*type == 'r') {
 107                         /*
 108                          * The _dup2() to STDIN_FILENO is repeated to avoid
 109                          * writing to pdes[1], which might corrupt the
 110                          * parent's copy.  This isn't good enough in
 111                          * general, since the _exit() is no return, so
 112                          * the compiler is free to corrupt all the local
 113                          * variables.
 114                          */
 115                         _close(pdes[0]);
 116                         if (pdes[1] != STDOUT_FILENO) {
 117                                 _dup2(pdes[1], STDOUT_FILENO);
 118                                 _close(pdes[1]);
 119                                 if (twoway)
 120                                         _dup2(STDOUT_FILENO, STDIN_FILENO);
 121                         } else if (twoway && (pdes[1] != STDIN_FILENO))
 122                                 _dup2(pdes[1], STDIN_FILENO);
 123                 } else {
 124                         if (pdes[0] != STDIN_FILENO) {
 125                                 _dup2(pdes[0], STDIN_FILENO);
 126                                 _close(pdes[0]);
 127                         }
 128                         _close(pdes[1]);
 129                 }
 130                 for (p = pidlist; p; p = p->next) {
 131                         _close(fileno(p->fp));
 132                 }
 133                 _execve(_PATH_BSHELL, __DECONST(char * const *, argv), environ);
 134                 _exit(127);
 135                 /* NOTREACHED */
 136         }
 137
 138         /* Parent; assume fdopen can't fail. */
 139         if (*type == 'r') {
 140                 iop = fdopen(pdes[0], type);
 141                 _close(pdes[1]);
 142         } else {
 143                 iop = fdopen(pdes[1], type);
 144                 _close(pdes[0]);
 145         }
 146
 147         /* Link into list of file descriptors. */
 148         cur->fp = iop;
 149         cur->pid =  pid;
 150         cur->next = pidlist;
 151         pidlist = cur;
 152
 153         return (iop);
 154 }
 155
 156 /*
 157  * pclose --
 158  *      Pclose returns -1 if stream is not associated with a `popened' command,
 159  *      if already `pclosed', or waitpid returns an error.
 160  */
 161 int
 162 pclose(FILE *iop)
 163 {
 164         struct pid *cur, *last;
 165         int pstat;
 166         pid_t pid;
 167
 168         /* Find the appropriate file pointer. */
 169         for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
 170                 if (cur->fp == iop)
 171                         break;
 172         if (cur == NULL)
 173                 return (-1);
 174
 175         fclose(iop);
 176
 177         do {
 178                 pid = _wait4(cur->pid, &pstat, 0, (struct rusage *)0);
 179         } while (pid == -1 && errno == EINTR);
 180
 181         /* Remove the entry from the linked list. */
 182         if (last == NULL)
 183                 pidlist = cur->next;
 184         else
 185                 last->next = cur->next;
 186         free(cur);
 187
 188         return (pid == -1 ? -1 : pstat);
 189 }