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Full Discussion: [C] execl and pipes?
Top Forums Programming [C] execl and pipes? Post 302584763 by Corona688 on Sunday 25th of December 2011 12:04:48 PM
Old 12-25-2011
Quote:
Originally Posted by lamachejo
The data is sent as an argument to the Master program. The data are two ints, one bigger than other (ex: 1000 and 2000).
Your program will likely crash or malfunction, since argv[0] is traditionally the name of the program, and the argument after the last one you give execl must be null, so try this:

Code:
const char *arg="/path/to/program";
execl(arg, arg, "1", "2", NULL);

Quote:
The problem is, when I fork, I know the fd are inherited in that process, but once I call the slave program with execl, I don't know how to connect the two programs with a pipe.
They already are. The copies of the pipe you get in the child talk to the same pipe. They're already joined. Write in the child, read in the parent. There's nothing else to be done (except closing the write-end in the parent, anyway. Don't leave extra ends around, they cause your program to freeze)
This User Gave Thanks to Corona688 For This Post:
lamachejo
 

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LEARN ABOUT HPUX

tels

tels(7) 						 Miscellaneous Information Manual						   tels(7)

NAME

       tels, telm - STREAMS Telnet slave (pseudo-terminal) driver, STREAMS Telnet master driver (used by telnetd only), respectively

SYNOPSIS


DESCRIPTION

       A  Telnet  pseudo-terminal  consists of a tightly-coupled pair of character devices, called the master device and slave device.	The master
       and slave device drivers work together to provide a Telnet connection on the server side where the master provides a connection to and  the
       slave provides a terminal device special file access for the Telnet application processes, as depicted below:

				--------------------------
			       | Pseudo terminal functions|
	      Application <--> |--------------------------| <--> telnetd
	       Processes       | Slave	    |	Master	  |
			       | (tels)     |	(telm)	  |
				--------------------------

       The  slave  driver, with (STREAMS pty emulation module) and (STREAMS line discipline module) pushed on top (not shown for simplicity), pro-
       vides a terminal interface as described in termio(7).  Whereas devices that provide the terminal interface described in	termio(7)  have  a
       hardware device behind them; in contrast, the slave device has manipulating it through the master side of the Telnet pseudo terminal.

       There  are no nodes in the file system for each individual master device.  Rather, the master driver is set up as a STREAMS clone(7) driver
       with its major device number set to the major for the clone driver and its minor device number set to the major for the driver.	The master
       driver is opened by telnetd using the open(2) system call with as the device file parameter.  The clone open finds the next available minor
       number for the master device.  The master device is available only if it and its corresponding slave device are not already opened.

       In order to use the STREAMS Telnet subsystem, a node for the master driver and N number of Telnet slave devices must be installed.

       The number of slave devices is set by a kernel tunable parameter called This can be modified using SAM; its default and	minimum  value	is
       60. The value of is the upper limit of the number of telnet sessions that can be opened.

       Multiple opens are allowed on the Telnet slave device.

       The  master  and  slave	drivers pass all STREAMS messages to their adjacent drivers.  When the connection is closed from the Telnet client
       side, an message is sent to the corresponding slave device which will render that slave device unusable.  The process  on  the  slave  side
       gets  the errno when attempting a write(2) system call to the slave device file but it will be able to read any data remaining in the slave
       stream.	Finally, when all the data has been read, the read(2) system call will return 0, indicating that the slave can no longer be used.

AUTHOR

       and were developed by HP.

FILES

       Streams Telnet master clone device

       Streams slave devices where
			   N is the minor number of the slave device and 0 < N <

SEE ALSO

       insf(1M), open(2), ioctl(2), streamio(7), ldterm(7), telnetd(1M), ptem(7).

																	   tels(7)
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