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cstream(1)		FreeBSD	General	Commands Manual		    cstream(1)

NAME
     cstream --	direct data streams, with bandwidth limiting, FIFO, audio, du-
     plication and extended reporting support.

SYNOPSIS
     cstream [-b num] [-B num] [-i filename] [-I string] [-l] [-n num]
	     [-o filename] [-O string] [-p filename] [-t num] [-T num]
	     [-v num] [-V] [filename]

DESCRIPTION
     Cstream filters data streams, much	like the UNIX tool dd(1).  It has a
     more traditional commandline syntax, support for precise bandwidth	limit-
     ing and reporting and support for FIFOs. Data limits and throughput rate
     calculation will work for files > 4 GB.

     Cstream reads from	the standard input and writes to the standard output,
     if	no filenames are given.	It will	also 'generate'	or 'sink' data if de-
     sired.

     Options:

     -b	num    Set the block size used for read/write to num.  The default is
	       8192 bytes.

     -B	num    Buffer input up to num bytes before writing. The	default	is the
	       blocksize. It is	an error to set	this to	anything below the
	       blocksize. Useful when writing tapes and	similar	that prefer
	       few large writes	of many	small.

     -c	num    Concurrent operation. Use a separate process for	output.	This
	       is especially useful in combination with	the -B option.
	       0 = use one process only	(default)
	       1 = read	process	will buffer
	       2 = write process will buffer
	       3 = both	processes will buffer.
		   In combination with a large buffer size this	will often
		   load	your memory heavily, every time	the reader transfers
		   the buffer it collected to the writer. If you use -c	3 and
		   have	a buffer size of 128 Megabytes 256 MB of memory	will
		   be touched at once.

     -i	num

     -o	num    Set the file names to use for input or output, respectively. If
	       the output file name is "-", data will just be discarded. If
	       the input file name is "-", data	will be	generated 'out of the
	       void'. If these options aren't given, stdin/stout will be used.
	       If you need to give -o or -i options and	want stdin/stdout,
	       specify the empty string, like this:

	       cstream -i''

	       If TCP support has been compiled	in (default), hostname:port-
	       number will try to connect to the specified host	at the speci-
	       fied port and :portnumber will open a TCP socket	on the local
	       machine and wait	for a connection to arrive. SECURITY NOTE:
	       cstream includes	no mechanism to	restrict the hosts that	may
	       connect to this port. Unless your machine has other network
	       filters,	anyone will be able to connect.

     -I	string

     -O	string
	       Specify the type	of input and output file, respectively.
	       If string
		   includes 'f', a fifo	will be	created.
	       If string
		   includes 'a', the file will be assumed to be	a opensound-
		   compatible audio device and will be switched	to CD-like
		   settings.
	       If string
		   includes 't', a copy	of the stream will be sent to file de-
		   scriptor 3.
	       If string
		   includes 'N', TCP will not be used for that file even if
		   the name has	a ":".

     -l	       Include line count in statistics.

     -n	num    Limit the total amount of data to num.  If there	is more	input
	       available, it will be discarded,	cstream	will exit after	the
	       limit has been reached. If there	is less	input, the limit will
	       not be reached and no error will	be signaled.

	       num may have a trailing 'k', 'm'	or 'g' which means Kilobytes,
	       Megabytes or Gigabytes (where Kilo = 1024). This	applies	to all
	       numeric options.

     -p	filename
	       Write the process id of cstream to filename.  If	cstream	uses a
	       separate	writer process (option -c), this is the	pid of the
	       parent (reader) process.

     -t	num    Limit the throughput of the data	stream to num bytes/second.
	       Limiting	is done	at the input side, you can rely	on cstream not
	       accepting more than this	rate. If the number you	give is	posi-
	       tive, cstream accumulates errors	and tries to keep the overall
	       rate at the specified value, for	the whole session. If you give
	       a negative number, it is	an upper limit for each	read/write
	       system call pair. In other words: the negative number will
	       never exceed that limit,	the positive number will exceed	it to
	       make good for previous underutilization.

     -T	num    Report throughput every num seconds.

     -v	num    Set verbose level to num.  By default, it is set	to 0, which
	       means no	messages are displayed as long as no errors occur. A
	       value of	1 means	that total amount of data and throughput will
	       be displayed at the end of program run. A value of 2 means the
	       transfer	rate since the end of the first	read/write pair	will
	       also be reported	(useful	when there is an initial delay). A
	       value of	3 means	there will also	be separate measurements for
	       read and	write. This option is resource-consuming and currently
	       isn't implemented. A value of 4 means that notices about	each
	       single read/write will be displayed. High values	include	all
	       message types of	lower values.

     -V	       Print version number to stdout and exit with 0.

     filename  A single	filename as the	last argument without an option	switch
	       will be used as input file if -i	has not	been used.

     SIGUSR1

     SIGINFO   Sending SIGUSR1 (or SIGINFO, which is usually mapped to Con-
	       trol-T on you keyboard) to cstream causes it to display
	       throughput rates	to stderr. The stream will continue as if
	       nothing happened.

     SIGUSR2   Exit and	report throughput rates, if requested.

     SIGHUP    I found myself sending SIGHUP accidentally too often. But ig-
	       noring or misusing SIGHUP is not	an option for me. Thus,	when
	       cstream received	SIGHUP,	it will	wait 5 seconds for another
	       SIGHUP, to give users a chance to correct a possible mistake.
	       If no additional	SIGHUP is received, cstream kills itself with
	       SIGHUP.

EXAMPLES
     cstream -o	tmpfile	-v 1 -n	384m -i	-
	     Writes 384	Megabytes of unspecified data to file tmpfile and dis-
	     play verbose throughput rate. Makes a good	benchmark, the speed
	     of	/dev/null varies too much from system to system.

     cstream -i	tmpfile	-v 1 -n	384m -o	-
	     Read the same file	back in	and discard data.

     cstream -b	2000  -t 10000 /var/log/messages
	     Will display the file in a	more or	less watchable speed.

     dump 0sf 400000 - / | cstream -v 1	-b 32768 -o /dev/rst0 -p pidfile

     kill -USR1	`cat pidfile`
	     Write the output from dump(1) to tape. Each time the signal is
	     sent, the throughput and data rate	so far will be displayed.

     cstream -t	176400 -i /dev/dsp0 -I f -o -
	     Makes kind	of a soundcard emulator	which may be used to test au-
	     dio applications that need	something to write to that limits the
	     data rate as a real soundcard does. This obviously	doesn't	work
	     when the application tries	to write data using mmap(2) and	the
	     application has to	ignore errors when it tries to set soundcard
	     parameters	using ioctl(2).

     cstream -t	176400 -i /dev/dsp0 -I f -o /dev/dsp1 -O f
	     Similar soundcard emulator, except	that it	allows you to grab the
	     data your applications sends to it	from the other fifo, while
	     still having precise timing.

     cstream -Oa -o /dev/dsp0 myhost.mydomain.com:17324
	     Connects port 3333	on host	myhost.mydomain.com and	whatever data
	     it	finds there will be sent to the	soundcard, with	appropriate
	     settings for CD quality stereo play.

     cstream -i	myaudiofile.raw	-o :17324
	     This will open a TCP server on port 17324 and waits until someone
	     connects (for example, the	commandline from the previous exam-
	     ple). Then	it will	send the contents of myaudiofile.raw down the
	     TCP stream	(for the previous audio	example, typically a CD	audio
	     track like	you get	from the tosha or cdparanoia utilities).

     cstream -OD -o myfile
	     Write to file myfile with O_DIRECT.  That usually means that the
	     filesystem	buffer cache will not try to cache this	file.  You can
	     use that to prevent copying operations from eating	up physical
	     memory.  Note that	when cstream encounters	a write	error it will
	     switch the	output file from O_DIRECT to a normal file and write
	     all further blocks	without	O_DIRECT if writes without O_DIRECT
	     succeed.  In practice that	usually	means that your	last block, if
	     not a multiple of the filesystem block size, will still be	writ-
	     ten into the file (the maximum amount of data written without
	     O_DIRECT is your blocksize	minus one).  That way cstream ensures
	     that the output file has the length of the	input, however odd the
	     length was	and no matter what restrictions	your OS	places on
	     O_DIRECT output.  Again, cstream will *not* pad the output	to the
	     block size, you get the same file and file	size as	if not using
	     O_DIRECT, at the cost of switching	to non-O_DIRECT	whenever a
	     block is not the right size.

     cstream -i	:3333 |	dd obs=8192 | ./cstream	-omyfile -v7 -OD
	     This is what you need to do to buffer TCP input, so that the last
	     cstream will not switch away from O_DIRECT	prematurely because of
	     short reads.  If your input can do	short reads (e.g. from TCP),
	     and you want to ensure that O_DIRECT stays	in effect, you need a
	     buffer between the	TCP stream and the O_DIRECT stream.  Since
	     cstream does not yet support different input and output block
	     sizes, dd is suitable here.  Note that this is only necessary if
	     the OS requires multiples of the filesystem block size for	O_DI-
	     RECT.  At the time	of this	writing	this construct is needed on
	     Linux for using TCP streams with O_DIRECT,	but it is not needed
	     on	FreeBSD.

     cstream -OS -o myfile
	     Writes to file myfile with	O_SYNC.	 This means by the time	the
	     system call returns the data is known to be on disk.  This	is not
	     the same thing as O_DIRECT.  O_DIRECT can do its own buffering,
	     with O_SYNC there is no buffering at all.	At the time of this
	     writing, O_SYNC on	both Linux and FreeBSD is very slow (1/5th to
	     1/10th of normal write) and O_DIRECT is reasonably	fast (1/4th to
	     1/2 of normal write).  You	can combined O_SYNC and	O_DIRECT.

ERRORS
     Exit code 0 means success.

     Exit code 1 means a commandline syntax usage error.

     Exit code 2 means other errors, especially	system errors.

Bugs
     There should be an	option to begin	writing	directly after the first read
     ended and then fill the buffer with reads in the background.  Right now
     writing will not begin before the reader has filled the buffer completely
     for the first time.

     Not a bug:	the code to do O_DIRECT	is reasonably sophisticated.  It will
     fall back to normal I/O on	errors.	 But before doing that it knows	about
     both filesystem blocksize requirements (will default I/O blocksize	to
     whatever the filesystem of	the output file	is in) and page	alignment re-
     quirements	(I/O will happen from a	page-aligned buffer).  However,	the
     combination of concurrent read/writes (-c options)	and O_DIRECT has not
     been tested beyond	basic verification that	it gets	some tests right.

SEE ALSO
     dd(1), mkfifo(2)

HISTORY
     cstream was initially written by Martin Cracauer in 1998.	For updates
     and more information see http://www.cons.org/cracauer/cstream.html

FreeBSD	13.0			March, 30, 1999			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | ERRORS | Bugs | SEE ALSO | HISTORY

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