compiler/clib/popen.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     POSIX.1-2008 function popen().
   6 */
   7
   8 #include <utility/tagitem.h>
   9 #include <proto/dos.h>
  10 #include <fcntl.h>
  11 #include <unistd.h>
  12
  13 #include "__fdesc.h"
  14
  15 #include <errno.h>
  16
  17
  18 /*****************************************************************************
  19
  20     NAME */
  21 #include <stdio.h>
  22
  23         FILE * popen (
  24
  25 /*  SYNOPSIS */
  26         const char * command,
  27         const char * mode)
  28
  29 /*  FUNCTION
  30         "opens" a process by creating a pipe, spawning a new process and invoking
  31         the shell.
  32
  33     INPUTS
  34         command - Pointer to a null terminated string containing the command
  35                   to be executed by the shell.
  36
  37         mode - Since a pipe is unidirectional, mode can be only one of
  38
  39                 r: Open for reading. After popen() returns, the stream can
  40                    be used to read from it, as if it were a normal file stream,
  41                    in order to get the command's output.
  42
  43                 w: Open for writing. After popen() returns, the stream can
  44                    be used to write to it, as if it were a normal file stream,
  45                    in order to provide the command with some input.
  46
  47     RESULT
  48         A pointer to a FILE handle or NULL in case of an error. When NULL
  49         is returned, then errno is set to indicate the error.
  50
  51     NOTES
  52         This function must not be used in a shared library or
  53         in a threaded application.
  54
  55     EXAMPLE
  56
  57     BUGS
  58
  59     SEE ALSO
  60         fclose(), fread(), fwrite(), pipe(), pclose()
  61
  62     INTERNALS
  63
  64 ******************************************************************************/
  65 {
  66     int pipefds[2];
  67
  68     if (!mode || (mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0')
  69     {
  70         errno = !mode ? EFAULT : EINVAL;
  71         return NULL;
  72     }
  73
  74     if (pipe(pipefds) == 0)
  75     {
  76         int fdtopass = (mode[0] == 'r');
  77
  78         struct TagItem tags[] =
  79         {
  80             { SYS_Input   , 0                                               },
  81             { SYS_Output  , 0                                               },
  82             { SYS_Error   , SYS_DupStream                                   },
  83             { SYS_Asynch  , TRUE                                            },
  84             { NP_StackSize, Cli()->cli_DefaultStack * CLI_DEFAULTSTACK_UNIT },
  85             { TAG_DONE    , 0                                               }
  86         };
  87
  88         tags[fdtopass].ti_Data     = (IPTR)__getfdesc(pipefds[fdtopass])->fcb->fh;
  89         tags[1 - fdtopass].ti_Data = SYS_DupStream;
  90
  91         if (SystemTagList(command, tags) != -1)
  92         {
  93             /* Little trick to deallocate memory which otherwise wouldn't get deallocated */
  94             __getfdesc(pipefds[fdtopass])->fcb->fh = BNULL;
  95             close(pipefds[fdtopass]);
  96
  97             return fdopen(pipefds[1 - fdtopass], NULL);
  98         }
  99
 100         close(pipefds[0]);
 101         close(pipefds[1]);
 102     }
 103
 104     return NULL;
 105 } /* popen */