Operating System Words

This section describes the words that interact with the underlying operating system that Until runs under.

( --- argc )
"a-r-g-c". argc leaves the number of arguments from the command line on the parameter stack. This makes passing command line arguments to Until words easy. See argv for a complete example.
( --- argv )
"a-r-g-v". argv leaves the pointer to the arguments on the command line on the stack. This makes passing command line arguments to Until words easy.
      : test-argv
           argv       20 dump cr cr
           argv @     20 dump cr cr ( argv[0] )
           argv 4 + @ 20 dump cr cr ( argv[1] )

( --- )
"dir". Executes a "dir" command to the OS. This works fine in DOS, CP/M, and VAX/VMS. In Unix and its' clones, you must create a shell script named dir. dir accepts no file specification. Do a directory via system to generate a selective directory.
( 'filename --- )
This word shells to the OS to execute the editor specified in the global variable editor. The default is EMACS, except for Coherent where the name is "me". Usage is:
      " filename" edit
Once the filename has been specified in the first edit, simply use here to edit the same file again.
( --- value )
"errno". Return the value of C's errno global variable to the top of the stack. Refer to your C compiler's documentation for values and their meanings.
( --- )
"f-load". Compile the sealed file specified as the next token in the input stream.
      fload source.bin

( addr --- )
"free". Return memory allocated by malloc to the system. See malloc for an example.
( 'env-string --- )
"get-e-n-v". Retrieves the system environment variable whose name is contained in 'env-string. The original value is replaced with the value returned by the system.
    80 string value
    value " UNTIL-DIR" strcpy
    value get_env
    value dup count type cr

( --- )
"include". Compiles the file specified as the next token in the input stream.
      include source.app
Compiles the file, source.app, then returns to normal interpretation of commands from the console.
( --- )
"list". Type the contents of a file. The usage is:
      list filename

( --- )
"load". Load is not implemented. See fload or include.
( n --- addr )
"malloc". Allocate n bytes of system memory. The C malloc() function is called. Use free to return the memory to the system when done with it. Usage:
      100 malloc
      mem_ptr !
      ( some words )
      mem_ptr @

( 'memory-block --- addr )
"re-alloc". Call the C function realloc() to reallocate a block of memory. memory-block is the address of a previously malloc'd block of memory. The return, addr, is either the address of the newly allocated memory block or 0 on error.
( --- )
"shell". Spawn/fork/whatever a shell to the OS.
Log off to exit the shell and return to Until. This is exit in DOS, Control-D in **ix, and logout in VMS.
( --- fd-stdin )
"standard-in". Leave the file descriptor on the stack for STDIN. Most systems open STDIN by default.
( --- fd-stdout )
"standard-out". Leave the file descriptor on the stack for STDOUT. Most systems open STDOUT by default.
( --- )
"system". Used in the form:
      " command" system

This command shells out to the operating system and executes the command, such as dir.

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