compiler/clib/popen.c

   1 /*
   2     Copyright © 1995-2003, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     ANSI C 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 "__stdio.h"
  14 #include "__open.h"
  15
  16 #include <errno.h>
  17
  18
  19 /*****************************************************************************
  20
  21     NAME */
  22 #include <stdio.h>
  23
  24         FILE * popen (
  25
  26 /*  SYNOPSIS */
  27         const char * command,
  28         const char * mode)
  29
  30 /*  FUNCTION
  31         "opens" a process by creating a pipe, spawning a new process and invoking
  32         the shell.
  33
  34     INPUTS
  35         command - Pointer to a null terminated string containing the command
  36                   to be executed by the shell.
  37
  38         mode - Since a pipe is unidirectional, mode can be only one of
  39
  40                 r: Open for reading. After popen() returns, the stream can
  41                    be used to read from it, as if it were a normal file stream,
  42                    in order to get the command's output.
  43
  44                 w: Open for writing. After popen() returns, the stream can
  45                    be used to write to it, as if it were a normal file stream,
  46                    in order to provide the command with some input.
  47
  48     RESULT
  49         A pointer to a FILE handle or NULL in case of an error. When NULL
  50         is returned, then errno is set to indicate the error.
  51
  52     NOTES
  53         This function must not be used in a shared library or
  54         in a threaded application.
  55
  56     EXAMPLE
  57
  58     BUGS
  59
  60     SEE ALSO
  61         fclose(), fread(), fwrite(), pipe(), pclose()
  62
  63     INTERNALS
  64
  65 ******************************************************************************/
  66 {
  67     int pipefds[2];
  68
  69     if (!mode || (mode[0] != 'r' && mode[0] != 'w') || mode[1] != '\0')
  70     {
  71         errno = !mode ? EFAULT : EINVAL;
  72         return NULL;
  73     }
  74
  75     if (pipe(pipefds) == 0)
  76     {
  77         int fdtopass = (mode[0] == 'r');
  78
  79         struct TagItem tags[] =
  80         {
  81             { SYS_Input   , NULL                                            },
  82             { SYS_Output  , NULL                                            },
  83             { SYS_Error   , SYS_DupStream                                   },
  84             { SYS_Asynch  , TRUE                                            },
  85             { NP_StackSize, Cli()->cli_DefaultStack * CLI_DEFAULTSTACK_UNIT },
  86             { TAG_DONE    , 0                                               }
  87         };
  88
  89         tags[fdtopass].ti_Data     = (IPTR)__getfdesc(pipefds[fdtopass])->fh;
  90         tags[1 - fdtopass].ti_Data = SYS_DupStream;
  91
  92         if (SystemTagList(command, tags) != -1)
  93         {
  94             /* Little trick to deallocate memory which otherwise wouldn't get deallocated */
  95             __getfdesc(pipefds[fdtopass])->fh = NULL;
  96             close(pipefds[fdtopass]);
  97
  98             return fdopen(pipefds[1 - fdtopass], NULL);
  99         }
 100
 101         close(pipefds[0]);
 102         close(pipefds[1]);
 103     }
 104
 105     return NULL;
 106 } /* popen */