main(3C)                   DG/UX 4.30                    main(3C)



     NAME
          main - Enter a C main program.

     SYNOPSIS
          main ([argc, argv, envp])
          int argc;
          char *argv[];
          char *envp[];
          {
          }


          where   argc is optional and is the number of arguments,
                  including the program name, with which you invoke
                  the C program.
                  argv is optional and is a pointer to an array of
                  pointers to strings; argv[0] is the name you invoked
                  the program with; argv[1] is the first argument on
                  the command line after the program name; argv[argc]
                  is a null pointer.
                  envp is optional and is a pointer to an array of
                  pointers to strings, each of which is a separate
                  environment variable of the form NAME = VALUE.  The
                  getenv function (described earlier in this chapter)
                  accesses this list of environment variables.  The
                  DG/UX system routines execle and execve can change
                  the environment of the new process if it is a C
                  program.


     DESCRIPTION
          Every C program has at least one function: the main
          function.  This function provides a place for the program to
          begin execution; the main function must be present to
          initiate a C program.  The runtime initializer calls main
          and returns to the system when main returns.

          Since argv[0] is the program name, the initial value of argc
          is always at least 1. If you want to manipulate the argv
          character arrays as something other than strings, you must
          make explicit use of such functions as atof or atoi.

          If your program does not process command line arguments,
          begin the function with the following:

          main()

     RETURNS
          The main function's return value is used as an argument to
          the exit function.  The value 0 typically means no errors
          occurred, and a non-zero value indicates an error condition.
          The wait function can retrieve this value.



     Licensed material--property of copyright holder(s)         Page 1

     main(3C)                   DG/UX 4.30                    main(3C)



     SEE ALSO
          getenv(3c), exec(2), exit(3c), wait(2), wait3(2).

     EXAMPLE
          /* Program test for the main() function */

          int  i = 1;

          main(argc, argv, envp)
          int     argc;
          char   *argv[];
          char   *envp[];
          {
              printf("You called the program %s.\n", argv[0]);
              while (i < argc) {
                  printf("Argument %d for this run is %s.\n",
                  i, argv[i]);
                  i++;
              }
          }

          A call to the program test with arguments alpha, beta, and
          gamma generates the output

          You called the program test.
          Argument 1 for this run is alpha.
          Argument 2 for this run is beta.
          Argument 3 for this run is gamma.



























     Licensed material--property of copyright holder(s)         Page 2