rexx/src/systemx.c

   1 /*-----------------------------------------------------------------------*
   2  * filename - systemx.c
   3  *
   4  * function(s)
   5  *    systemx - issues an MS-DOS command
   6  *      and returns the command return code
   7  *-----------------------------------------------------------------------*/
   8
   9 #include <dos.h>
  10 #include <errno.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13
  14 /* ------------- function prototypes ------------- */
  15 static char *BDOSenv(char **envV, char *pathP, void **envSave);
  16 int cdecl far _spawnx(char  far *__path, char  far *__cmd, char far *__env);
  17 /* ------------- external variables -------------- */
  18 extern  void    cdecl (*_exitbuf)(void);
  19
  20 /* ------------------ systemx -------------------- */
  21 int far
  22 systemx(const char far *cmd)
  23 {
  24         char    *cmdP;
  25         int     cmdS;
  26         char    *envP;
  27         void    *envSave;
  28         char    *pathP;
  29         int     rc;
  30
  31 //  Get COMMAND.COM path from COMSPEC
  32
  33         if ((pathP = getenv("COMSPEC")) == NULL) {
  34                 errno = ENOENT;
  35                 return (-1);
  36         }
  37
  38 //  Build command line "LEN /C cmd\r"
  39
  40         cmdS = 1 + 3 + strlen(cmd) + 1;
  41         if (cmdS > 128) {
  42                 errno = E2BIG;
  43                 return (-1);
  44         }
  45         if ((cmdP = malloc(cmdS)) == NULL) {
  46                 errno = ENOMEM;
  47                 return (-1);
  48         }
  49
  50         if (cmdS == 5) {
  51                 cmdP[0] = 0;
  52                 cmdP[1] = '\r';
  53         } else {
  54                 *cmdP++ = cmdS - 2;
  55                 *cmdP++ = getswitchar();
  56                 cmdP = _stpcpy(cmdP, "c ");
  57                 cmdP = _stpcpy(cmdP, cmd);
  58                 *cmdP++ = '\r';
  59                 cmdP -= cmdS;
  60         }
  61
  62 //  Build environment for cmd
  63
  64         if ((envP = BDOSenv(environ, pathP, &envSave)) == NULL) {
  65                 errno = ENOMEM;
  66                 free(cmdP);
  67                 return (-1);
  68         }
  69
  70 //  Flush all byte streams before calling cmd
  71
  72         (*_exitbuf)();
  73
  74 //  Now, call the low level _spawnx function
  75
  76         rc = _spawnx(pathP, cmdP, envP);
  77
  78 //  Release all buffers, and exit
  79
  80         free(envSave);
  81         free(cmdP);
  82         return (rc);
  83 } /* systemx */
  84
  85 /* ------------------ BDOSenv -------------------- */
  86 //Description     This function allocates  a buffer and fill it  with all the
  87 //                environment  strings one  after  the  others. If  the pathP
  88 //                variable is nonzero, then it is  appended to the end of the
  89 //                end of  the environment assumed it  is for a spawn  or exec
  90 //                purpose.
  91 //
  92 //Return value    BDOSenv  returns a  pointer  to  the environment  buffer if
  93 //                successful, and NULL on error.
  94 //----------------------------------------------------
  95 static char *
  96 BDOSenv(char **envV, char *pathP, void **envSave)
  97 {
  98         char    **envW;
  99         unsigned        envS;
 100         char    *bufP;
 101
 102 //      Compute the environment size including  the NULL string at the
 103 //      end of the environment. (Environment size < 32 Kbytes)
 104
 105         envS = 1;
 106         if ((envW = envV) != NULL)
 107         for (envS = 0; *envW && **envW; envS += strlen(*envW++) + 1) ;
 108         envS++;
 109         if (pathP)
 110                 envS += 2 + strlen(pathP) + 1;
 111         if (envS >= 0x2000)
 112                 return (NULL);
 113
 114 //      Allocate a buffer
 115
 116         if ((bufP = malloc(envS + 15)) != NULL) {
 117
 118 //              The environment MUST be paragraph aligned
 119 //
 120                 *envSave = bufP;
 121                 bufP += 15;
 122                 (*((unsigned *)&(bufP))) &= 0xFFF0;
 123
 124 //              Concatenate all environment strings
 125 //
 126                 if ((envW = envV) != NULL && *envW != NULL)
 127                         while (*envW && **envW) {
 128                                 bufP = _stpcpy(bufP, *envW++);
 129                                 *bufP++ = '\0';
 130                 } else
 131                         *bufP++ = '\0';
 132                 *bufP++ = '\0';
 133
 134 //              Append program name to the environment
 135 //
 136                 if (pathP) {
 137                         *((short *)bufP)++ = 1;
 138                         bufP = _stpcpy(bufP, pathP);
 139                         *bufP++ = '\0';
 140                 }
 141                 return bufP - envS;
 142         } else
 143                 return NULL;
 144 } /* BDOSenv */