On Mon, Sep 26, 2011 at 3:57 PM, Ludwig Isaac Lim <[email protected]> wrote: > Hi: > Thanks for the quick response. Since according to definition of line > buffering (see below), a buffer is flushed is after newlines, so writing > statements such as : > print "<p> This is a paragraph</p>\n" > > in a CGI program will automatically flush the buffer right? Or it > doesn't? I wondering if perl will figure out that since STDOUT is not > connected to a terminal, it will still buffer it even though the print > contains a newline.
hi ludwig, you need to understand the buffering system of standard i/o library.. there are 3 kinds of buffering.. 1. fully buffered 2. line bufffered 3. unbuffered the goal of buffering is to minimize number of read and write expensive system calls... in fully buffered.. actual i/o takes place when allocated buffer is filled... for example files in a disk are normally fully buffered.. when you read data from a file.. data from kernel land to user land delivered when bufer is filled... when you write a data to a file.. disk write takes place (flush) when buffer is filled.. in line buffered.. actual i/o takes place either allocated buffer is filled or new line character is encountered on input or output stream whichever comes first... for example interactive device such as terminal device is normally line buffered.. in unbuffered.. i/o takes place immediately... for example.. standard error is normally unbuffered... error messages are displayed as soon and quickly as possible... ANSI C requiers the following buffering characteristics... 1. standard input and standard output are fully buffered as long as they do not refer to an interactive device.. 2. standard error is never fully buffered... in your CGI program... if you run that in interactive mode... print command is line buffered because standard output is connected to a terminal device.... if you run that as a server and output connected to a socket... it is a fully buffered because socket is fully buffered.. if you dont like these defaults of any given standard i/o stream or you want to change its characteristic from fully buffered to line buffered for example.. you can use "setvbuf" function call and specify the mode you want... _IOFBF = fully buffered _IOLBF = line buffered _IONBF = unbuffered $| is equivalent to line buffered as it flushes after write or print command.. fooler. _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List http://lists.linux.org.ph/mailman/listinfo/plug Searchable Archives: http://archives.free.net.ph
