Section for Week 8, Tuesday, 3/2/99

Sixth HW solutions is posted.

1.  SSI & CGI
    SS-Include: Syntax:
	<!--#include file="filename.html">
	Uses? (footers, headers, standard forms, etc)
	
    SS-Exec: Syntax:
	<!--#exec cgi="script.cgi">
	Uses? 
	Make sure to output a valid Content-type line like always, but this
	time no HTML header info is necessary (output will be merged into
	the parent .shtml file in place of the tag).
	
    Redirects:
	Instead of Content-type line, if a line like:
	Location: otherfile.html
	
	is the first line in the output of your CGI, then the server will
	instead serve the otherfile.html file.

2.  flock()
    Why use it?  
    When (in the program) do you use it?
    How do you use it?  
	flock FH, CODE
      Where FH is a filehandle, and CODE is: 
      1 -> LOCK_SH  Shared lock
      2 -> LOCK_EX  Exclusive lock
      4 -> LOCK_NB  Nonblocking -- add to either SH or EX to make non-blocking
      8 -> LOCK_UN  Unlock (alt. can just close() the filehandle).

    What are shared locks good for?  (prevent ex locks, only for reading)
    Check return code of NB call to see whether got the lock