1cstream(1) BSD General Commands Manual cstream(1)
2
4 cstream — direct data streams, with bandwidth limiting, FIFO, audio,
5 duplication and extended reporting support.
6
8 cstream [-b num] [-B num] [-i filename] [-I string] [-l] [-n num]
9 [-o filename] [-O string] [-p filename] [-t num] [-T num]
10 [-v num] [-V] [filename]
11
13 Cstream filters data streams, much like the UNIX tool dd(1). It has a
14 more traditional commandline syntax, support for precise bandwidth limit‐
15 ing and reporting and support for FIFOs. Data limits and throughput rate
16 calculation will work for files > 4 GB.
17 Cstream reads from the standard input and writes to the standard output,
19 if no filenames are given. It will also 'generate' or 'sink' data if
20 desired.
21 Options:
23 -b num Set the block size used for read/write to num. The default is
25 8192 bytes.
26 FIXME: The buffer size logic inside cstream is broken.
27 -B num Buffer input up to num bytes before writing. The default is the
29 blocksize. It is an error to set this to anything below the
30 blocksize. Useful when writing tapes and simlilar that prefer
31 few large writes of many small.
32 FIXME: The buffer size logic inside cstream is broken.
33 -c num Concurrent operation. Use a seperate process for outout. This
35 is especially useful in combination with the -B option.
36 0 = use one process only (default)
37 1 = read process will buffer
38 2 = write process will buffer
39 3 = both processes will buffer.
40 In combination with a large buffer size this will often
41 load your memory heavily, everytime the reader transfers
42 the buffer it collected to the writer. If you use -c 3 and
43 have a buffer size of 128 Megabytes 256 MB of memory will
44 be touched at once.
45 -i num
47 -o num Set the file names to use for input or output, respectivly. If
49 the output file name is "-", data will just be discarded. If
50 the input file name is "-", data will be generated 'out of the
51 void'. If these options aren't given, stdin/stout will be used.
52 If you need to give -o or -i options and want stdin/stdout,
53 specify the empty string, like this:
54 cstream -i''
56 If TCP support has been compiled in (default), hostname:port‐
58 number will try to connect to the specified host at the speci‐
59 fied port and :portnumber will open a TCP socket on the local
60 machine and wait for a connection to arrive. SECURITY NOTE:
61 cstream includes no mechanism to restrict the hosts that may
62 connect to this port. Unless your machine has other network
63 filters, anyone will be able to connect.
64 -I string
66 -O string
68 Specify the type of input and output file, respectivly.
69 If string
70 includes 'f', a fifo will be created.
71 If string
72 includes 'a', the file will be assumed to be a opensound-
73 compatible audio device and will be switched to CD-like
74 settings.
75 If string
76 includes 't', a copy of the stream will be sent to file
77 descriptor 3.
78 If string
79 includes 'N', TCP will not be used for that file even if
80 the name has a ":".
81 -l Include line count in statistics.
83 -n num Limit the total amount of data to num. If there is more input
85 available, it will be discarded, cstream will exit after the
86 limit has been reached. If there is less input, the limit will
87 not be reached and no error will be signaled.
88 num may have a trailing 'k', 'm' or 'g' which means Kilobytes,
90 Megabytes or Gigabytes (where Kilo = 1024). This applies to all
91 numeric options.
92 -p filename
94 Write the process id of cstream to filename. If cstream uses a
95 seperate writer process (option -c), this is the pid of the
96 parent (reader) process.
97 -t num Limit the throughput of the data stream to num bytes/second.
99 Limiting is done at the input side, you can rely on cstream not
100 accepting more than this rate. If the number you give is posi‐
101 tive, cstream accumulates errors and tries to keep the overall
102 rate at the specified value, for the whole session. If you give
103 a negative number, it is an upper limit for each read/write
104 system call pair. In other words: the negative number will
105 never exceed that limit, the positive number will exceed it to
106 make good for previous underutilization.
107 -T num Report throughput every num seconds.
109 -v num Set verbose level to num. By default, it is set to 0, which
111 means no messages are displayed as long as no errors occur. A
112 value of 1 means that total amount of data and throughput will
113 be displayed at the end of program run. A value of 2 means the
114 transfer rate since the end of the first read/write pair will
115 also be reported (useful when there is an initial delay). A
116 value of 3 means there will also be seperate measurements for
117 read and write. This option is resource-consuming and currently
118 isn't implemented. A value of 4 means that notices about each
119 single read/write will be displayed. High values include all
120 message types of lower values.
121 -V Print version number to stdout and exit with 0.
123 filename A single filename as the last argument without an option switch
125 will be used as input file if -i has not been used.
126 SIGUSR1
128 SIGINFO Sending SIGUSR1 (or SIGINFO, which is usually mappend to Con‐
130 trol-T on you keyboard) to cstream causes it to display
131 throughput rates to stderr. The stream will continue as if
132 nothing happend.
133 SIGUSR2 Exit and report throughput rates, if requested.
135 SIGHUP I found myself sending SIGHUP accidentially too often. But
137 ignoring or misusing SIGHUP is not an option for me. Thus, when
138 cstream received SIGHUP, it will wait 5 seconds for another
139 SIGHUP, to give users a chance to correct a possible mistake.
140 If no additional SIGHUP is received, cstream kills itself with
141 SIGHUP.
142
144 cstream -o tmpfile -v 1 -n 384m -i -
145 Writes 384 Megabytes of unspecified data to file tmpfile and dis‐
146 play verbose throughput rate. Makes a good benchmark, the speed
147 of /dev/null varies too much from system to system.
148 cstream -i tmpfile -v 1 -n 384m -o -
150 Read the same file back in and discard data.
151 cstream -b 2000 -t 10000 /var/log/messages
153 Will display the file in a more or less watchable speed.
154 dump 0sf 400000 - / | cstream -v 1 -b 32768 -o /dev/rst0 -p pidfile
156 kill -USR1 `cat pidfile`
158 Write the output from dump(1) to tape. Each time the signal is
159 sent, the throughput and data rate so far will be displayed.
160 cstream -t 176400 -i /dev/dsp0 -I f -o -
162 Makes kind of a soundcard emulator which may be used to test
163 audio applications that need something to write to that limits
164 the data rate as a real soundcard does. This obviously doesn't
165 work when the application tries to write data using mmap(2) and
166 the application has to ignore errors when it tries to set sound‐
167 card parameters using ioctl(2).
168 cstream -t 176400 -i /dev/dsp0 -I f -o /dev/dsp1 -O f
170 Similar soundcard emulator, except that it allows you to grab the
171 data your applications sends to it from the other fifo, while
172 still having precise timing.
173 cstream -Oa -o /dev/dsp0 myhost.mydomain.com:17324
175 Connects port 3333 on host myhost.mydomain.com and whatever data
176 it finds there will be sent to the soundcard, with appropriate
177 settings for CD quality stero play.
178 cstream -i myaudiofile.raw -o :17324
180 This will open a TCP server on port 17324 and waits until someone
181 connects (for example, the commandline from the previous exam‐
182 ple). Then it will send the contents of myaudiofile.raw down the
183 TCP stream (for the previous audio example, typically a CD audio‐
184 track like you get from the tosha or cdparanoia utilities).
185 cstream -OD -o myfile
187 Write to file myfile with O_DIRECT. That usually means that the
189 filesystem buffer cache will not try to cache this file. You can
190 use that to prevent copying operations from eating up physical
191 memory. Note that when cstream encouters a write error it will
192 switch the output file from O_DIRECT to a normal file and write
193 all further blocks without O_DIRECT if writes without O_DIRECT
194 succeed. In practice that usually means that your last block, if
195 not a multiple of the filesystem block size, will still be writ‐
196 ten into the file (the maximum amount of data written without
197 O_DIRECT is your blocksize minus one). That way cstream ensures
198 that the output file has the length of the input, however odd the
199 length was and no matter what restrictions your OS places on
200 O_DIRECT output. Again, cstream will *not* pad the output to the
201 block size, you get the same file and file size as if not using
202 O_DIRECT, at the cost of switching to non-O_DIRECT whenever a
203 block is not the right size.
204 cstream -i :3333 | dd obs=8192 | ./cstream -omyfile -v7 -OD
206 This is what you need to do to buffer TCP input, so that the last
207 cstream will not switch away from O_DIRECT prematurely because of
208 short reads. If your input can do short reads (e.g. from TCP),
209 and you want to ensure that O_DIRECT stays in effect, you need a
210 buffer between the TCP stream and the O_DIRECT stream. Since
211 cstream does not yet support different input and output block
212 sizes, dd is suitable here. Note that this is only neccessary if
213 the OS requires multiples of the filesystem block size for
214 O_DIRECT. At the time of this writing this construct is needed
215 on Linux for using TCP streams with O_DIRECT, but it is not
216 needed on FreeBSD.
217 cstream -OS -o myfile
219 Writes to file myfile with O_SYNC. This means by the time the
220 system call returns the data is known to be on disk. This is not
221 the same thing as O_DIRECT. O_DIRECT can do its own buffering,
222 with O_SYNC there is no buffering at all. At the time of this
223 writing, O_SYNC on both Linux and FreeBSD is very slow (1/5th to
224 1/10th of normal write) and O_DIRECT is reasonably fast (1/4th to
225 1/2 of normal write). You can combined O_SYNC and O_DIRECT.
226
228 Exit code 0 means success.
229 Exit code 1 means a commandline syntax usage error.
231 Exit code 2 means other errors, especially system errors.
233
235 There should be an option to begin writing directly after the first read
236 ended and then fill the buffer with reads in the background. Right now
237 writing will not begin before the reader has filled the buffer completely
238 for the first time.
239 Not a bug: the code to do O_DIRECT is reasonably sophisticated. It will
241 fall back to normal I/O on errors. But before doing that it knows about
242 both filesystem blocksize requirements (will default I/O blocksize to
243 whatever the filesystem of the output file is in) and page alignment
244 requirements (I/O will happen from a page-aligned buffer). However, the
245 combination of concurrent read/writes (-c options) and O_DIRECT has not
246 been tested bejond basic verification that it gets some tests right.
247
249 dd(1), mkfifo(2)
250
252 cstream was initially written by Martin Cracauer in 1998. For updates
253 and more information see http://www.cons.org/cracauer/cstream.html
254BSD March, 30, 1999 BSD