* popen.scm, slib.scm: Added some docstrings for procedures that

were primitives that I encountered in posix.texi.

ice-9/popen.scm

@@ -40,6 +40,10 @@
 		   pid))))))
 
 (define-public (open-pipe command mode)
+  "Executes the shell command @var{command} (a string) in a subprocess.
+A pipe to the process is created and returned.  @var{modes} specifies
+whether an input or output pipe to the process is created: it should 
+be the value of @code{OPEN_READ} or @code{OPEN_WRITE}."
   (let* ((port/pid (open-process mode "/bin/sh" "-c" command))
 	 (port (car port/pid)))
     (pipe-guardian port)
@@ -56,6 +60,9 @@
   (cdr (waitpid (cdr port/pid))))
 
 (define-public (close-pipe p)
+  "Closes the pipe created by @code{open-pipe}, then waits for the process
+to terminate and returns its status value, @xref{Processes, waitpid}, for
+information on how to interpret this value."
   (let ((pid (fetch-pid p)))
     (if (not pid)
         (error "close-pipe: pipe not in table"))

ice-9/slib.scm

@@ -212,7 +212,18 @@
 			  '*sc-expander*
 			  '(define)))
 
-(define (software-type) 'UNIX)
+(define (software-type)
+  "Return a symbol describing the current platform's operating system.
+This may be one of AIX, VMS, UNIX, COHERENT, WINDOWS, MS-DOS, OS/2,
+THINKC, AMIGA, ATARIST, MACH, or ACORN.
+
+Note that most varieties of Unix are considered to be simply \"UNIX\".
+That is because when a program depends on features that are not present
+on every operating system, it is usually better to test for the presence
+or absence of that specific feature.  The return value of
+@code{software-type} should only be used for this purpose when there is
+no other easy or unambiguous way of detecting such features."
+ 'UNIX)
 
 (slib:load (in-vicinity (library-vicinity) "require.scm"))