newlib/libc/posix/popen.c

   1 /*      $NetBSD: popen.c,v 1.11 1995/06/16 07:05:33 jtc Exp $   */
   2
   3 /*
   4  * Copyright (c) 1988, 1993, 2006
   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  * 4. 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 /*
  36 FUNCTION
  37 <<popen>>, <<pclose>>---tie a stream to a command string
  38
  39 INDEX
  40         popen
  41 INDEX
  42         pclose
  43
  44 SYNOPSIS
  45         #include <stdio.h>
  46         FILE *popen(const char *<[s]>, const char *<[mode]>);
  47
  48         int pclose(FILE *<[f]>);
  49
  50 DESCRIPTION
  51 Use <<popen>> to create a stream to a child process executing a
  52 command string <<*<[s]>>> as processed by <</bin/sh>> on your system.
  53 The argument <[mode]> must start with either `<<r>>', where the stream
  54 reads from the child's <<stdout>>, or `<<w>>', where the stream writes
  55 to the child's <<stdin>>.  As an extension, <[mode]> may also contain
  56 `<<e>>' to set the close-on-exec bit of the parent's file descriptor.
  57 The stream created by <<popen>> must be closed by <<pclose>> to avoid
  58 resource leaks.
  59
  60 Streams created by prior calls to <<popen>> are not visible in
  61 subsequent <<popen>> children, regardless of the close-on-exec bit.
  62
  63 Use ``<<system(NULL)>>'' to test whether your system has <</bin/sh>>
  64 available.
  65
  66 RETURNS
  67 <<popen>> returns a file stream opened with the specified <[mode]>,
  68 or <<NULL>> if a child process could not be created.  <<pclose>>
  69 returns -1 if the stream was not created by <<popen>> or if the
  70 application used <<wait>> or similar to steal the status; otherwise
  71 it returns the exit status of the child which can be interpreted
  72 in the same manner as a status obtained by <<waitpid>>.
  73
  74 PORTABILITY
  75 POSIX.2 requires <<popen>> and <<pclose>>, but only specifies a mode
  76 of just <<r>> or <<w>>.  Where <<sh>> is found is left unspecified.
  77
  78 Supporting OS subroutines required: <<_exit>>, <<_execve>>, <<_fork_r>>,
  79 <<_wait_r>>, <<pipe>>, <<fcntl>>, <<sbrk>>.
  80 */
  81
  82 #ifndef _NO_POPEN
  83
  84 #if defined(LIBC_SCCS) && !defined(lint)
  85 #if 0
  86 static char sccsid[] = "@(#)popen.c     8.1 (Berkeley) 6/4/93";
  87 #else
  88 static char rcsid[] = "$NetBSD: popen.c,v 1.11 1995/06/16 07:05:33 jtc Exp $";
  89 #endif
  90 #endif /* LIBC_SCCS and not lint */
  91
  92 #include <sys/param.h>
  93 #include <sys/types.h>
  94 #include <sys/wait.h>
  95
  96 #include <signal.h>
  97 #include <errno.h>
  98 #include <unistd.h>
  99 #include <stdio.h>
 100 #include <stdlib.h>
 101 #include <string.h>
 102 #include <paths.h>
 103 #include <fcntl.h>
 104
 105 static struct pid {
 106         struct pid *next;
 107         FILE *fp;
 108         pid_t pid;
 109 } *pidlist;
 110
 111 FILE *
 112 popen (const char *program,
 113         const char *type)
 114 {
 115         struct pid *cur;
 116         FILE *iop;
 117         int pdes[2], pid;
 118
 119        if ((*type != 'r' && *type != 'w')
 120            || (type[1]
 121 #ifdef HAVE_FCNTL
 122                && (type[2] || (type[1] != 'e'))
 123 #endif
 124                                )) {
 125                 errno = EINVAL;
 126                 return (NULL);
 127         }
 128
 129         if ((cur = malloc(sizeof(struct pid))) == NULL)
 130                 return (NULL);
 131
 132         if (pipe(pdes) < 0) {
 133                 free(cur);
 134                 return (NULL);
 135         }
 136
 137         switch (pid = vfork()) {
 138         case -1:                        /* Error. */
 139                 (void)close(pdes[0]);
 140                 (void)close(pdes[1]);
 141                 free(cur);
 142                 return (NULL);
 143                 /* NOTREACHED */
 144         case 0:                         /* Child. */
 145                 if (*type == 'r') {
 146                         if (pdes[1] != STDOUT_FILENO) {
 147                                 (void)dup2(pdes[1], STDOUT_FILENO);
 148                                 (void)close(pdes[1]);
 149                         }
 150                         if (pdes[0] != STDOUT_FILENO) {
 151                                 (void) close(pdes[0]);
 152                         }
 153                 } else {
 154                         if (pdes[0] != STDIN_FILENO) {
 155                                 (void)dup2(pdes[0], STDIN_FILENO);
 156                                 (void)close(pdes[0]);
 157                         }
 158                         (void)close(pdes[1]);
 159                 }
 160                 /* Close all fd's created by prior popen.  */
 161                 for (cur = pidlist; cur; cur = cur->next)
 162                         (void)close (fileno (cur->fp));
 163                 execl(_PATH_BSHELL, "sh", "-c", program, NULL);
 164                 _exit(127);
 165                 /* NOTREACHED */
 166         }
 167
 168         /* Parent; assume fdopen can't fail. */
 169         if (*type == 'r') {
 170                 iop = fdopen(pdes[0], type);
 171                 (void)close(pdes[1]);
 172         } else {
 173                 iop = fdopen(pdes[1], type);
 174                 (void)close(pdes[0]);
 175         }
 176
 177 #ifdef HAVE_FCNTL
 178         /* Mark pipe cloexec if requested.  */
 179         if (type[1] == 'e')
 180                 fcntl (fileno (iop), F_SETFD,
 181                        fcntl (fileno (iop), F_GETFD, 0) | FD_CLOEXEC);
 182 #endif /* HAVE_FCNTL */
 183
 184         /* Link into list of file descriptors. */
 185         cur->fp = iop;
 186         cur->pid =  pid;
 187         cur->next = pidlist;
 188         pidlist = cur;
 189
 190         return (iop);
 191 }
 192
 193 /*
 194  * pclose --
 195  *      Pclose returns -1 if stream is not associated with a `popened' command,
 196  *      if already `pclosed', or waitpid returns an error.
 197  */
 198 int
 199 pclose (FILE *iop)
 200 {
 201         register struct pid *cur, *last;
 202         int pstat;
 203         pid_t pid;
 204
 205         (void)fclose(iop);
 206
 207         /* Find the appropriate file pointer. */
 208         for (last = NULL, cur = pidlist; cur; last = cur, cur = cur->next)
 209                 if (cur->fp == iop)
 210                         break;
 211         if (cur == NULL)
 212                 return (-1);
 213
 214         do {
 215                 pid = waitpid(cur->pid, &pstat, 0);
 216         } while (pid == -1 && errno == EINTR);
 217
 218         /* Remove the entry from the linked list. */
 219         if (last == NULL)
 220                 pidlist = cur->next;
 221         else
 222                 last->next = cur->next;
 223         free(cur);
 224
 225         return (pid == -1 ? -1 : pstat);
 226 }
 227
 228 #endif  /* !_NO_POPEN  */