CW(1) | General Commands Manual | CW(1) |
cw - sound characters as Morse code on the soundcard or console speaker
cw [-s --system=SYSTEM] [-d --device=DEVICE] [-w --wpm=WPM] [-t --tone=HZ] [-v --volume=PERCENT] [-g --gap=GAP] [-k --weighting=WEIGHT] [-e --noecho] [-m --nomessages] [-c --nocommands] [-o --nocombinations] [-p --nocomments] [-f --infile=FILE] [-h --help] [-V --version]
cw installed on GNU/Linux systems understands both short form and long form command line options. cw installed on other operating systems may understand only the short form options.
There are no mandatory options.
Options may be predefined in the environment variable CW_OPTIONS. If defined, these options are used first; command line options take precedence.
cw reads characters from an input file, or from standard input, and sounds each valid character as Morse code on either the system sound card, or the system console speaker. After it sounds a character, cw echoes it to standard output. The input stream can contain embedded command strings. These change the parameters used when sounding the Morse code. cw reports any errors in embedded commands on standard error.
Use 'Ctrl+D' key combination to exit cw.
cw understands the following command line options. The long form options may not be available in non-LINUX versions.
cw reads characters, one at a time, from its standard input or from its input file. Lowercase letters are converted internally to uppercase. The following list shows the valid IS0 8859-1 (Latin-1) characters that can be sounded by cw:
In addition, the program also understands the following ISO 8859-1 and ISO 8859-2 accented characters:
and accepts the following as single character forms of common procedural signals:
See cw(7,LOCAL) for more information on the above characters and Morse code.
If cw receives a character not in this set, it prints an error message '?c', where c is the error character. The only exceptions to this may be the cw command escape character '%', the combination start and stop characters '[' and ']', and the comment start and stop characters '{' and '}'. See EMBEDDED COMMANDS and MORSE CODE COMBINATIONS below.
cw recognizes special sequences in the input stream as embedded commands. These commands alter the parameters of the cw while it is running, or query current values. All commands are prefixed by the command escape character '%', and those which set a value end with a semicolon.
The format of an embedded command to change a parameter value is
where C is a command letter indicating what action cw is to take, and value is the argument or value for the command.
Valid command letters are
For example, the embedded command sequence
will set cw to a speed of 25 WPM, and a tone pitch of 1200Hz.
The 'T', 'W', 'G', and 'A' commands take values along with the command. The limits on values given for embedded commands are the same as the limits available for command line options, detailed above.
The 'E', 'M', 'S', 'C' and 'O' commands are flags, and treat a value of zero as clear, and any other value as set. So, for example, the sequence
will turn off error messages, and then turn off the processing of embedded commands.
If a parameter is set successfully, cw reports the new setting on standard error (except if no error messages is set). If an error is detected in an embedded command, cw reports an error. For the formats of error messages see the MESSAGE FORMATS section below.
The current values of parameters within cw may be queried, as well as set. The command format
queries the value of the parameter normally set with command C. cw reports the current value on standard error, using the same format as when new values are set.
The current values of parameters within cw may also be requested as output in Morse code. The command format
will generate Morse output reporting the value of the parameter normally set with command C.
If embedded commands are disabled, '%' characters are treated as any other (in this case, invalid) input character.
Once processing of embedded commands has been switched off, any command to switch this feature back on will not be recognized. That is, after '%C0;', an '%C1;' will not be recognized.
There is one additional command, and that is '%Q'. This command closes all open files and terminates cw. Any characters after this command in the input stream will be lost.
The file cw.h provides a full set of definitions for the commands, special characters, and status codes of cw.
Where a parameter value is set correctly with an embedded command, the message format
is returned. C is the command used, and value is the new value.
If an invalid value is supplied for a parameter in an embedded command, a message
is returned.
Where an invalid command is encountered, the message format
is used. For an invalid query, the message is
and for an invalid request for a parameter in Morse code the message is
A character in the input stream that cannot be sounded produces a message
These messages are not intended to be user-friendly, but are designed to be easily and quickly interpreted by another program. Similarly, the format of embedded commands is more computer-friendly than user-friendly.
If error messages are disabled, no messages of any type are printed on standard error.
The standard set of characters offered by cw may not be sufficient for some purposes. For example, some international characters do not have equivalent ISO 8859-1 and ISO 8859-2 that cw can sound directly.
To help in sounding such characters, cw offers the ability to form combination characters by placing individual character components between [...] brackets. Cw sounds characters inside a combination without the usual gap between them. In this way, any missing character in the set can be built.
For example
is one way to form the VA procedural signal, though
works just as well. The eight-dot error signal can be sounded with
or the C-cedilla in international Morse code with
There can be as many valid letters, numbers, or figures inside the [...] brackets as required. For example, an alternative way of sending the error signal could be
Finally, three alternative ways of sending 73 might be
Embedded commands may be placed inside [...] combinations if required. Combinations do not nest.
This feature can be disabled by using the -O or --nocombinations command line flags, or with the 'O' embedded command. If combinations are disabled, '[' and ']' characters are treated as any other (invalid) input character.
By default, cw tries to open default PulseAudio. If PulseAudio server is not accessible, cw tries to open OSS device "/dev/audio" to access the system sound card. This is generally the correct device to use, but for systems with special requirements, or those with multiple sound cards, the option -d or --device, combined with -s or --system can be used to specify the device and audio system for sound card access. If the sound card device cannot be set up, cw prints the error message
and exits.
Sound card devices, when opened through OSS sound system, are usually single-access devices, so that when one process has opened the device, other processes are prevented from using it. In such cases cw will of course conflict with any other programs that expect exclusive use of the system sound card (for example, MP3 players). If cw finds that the sound card is already busy, it prints the error message
and exits.
The sound card device is not used if cw is only sending tones on the console speaker.
cw first tries to access sound card using PulseAudio sound system, using default device name, unless user specifies other audio device with option -d or --device.
cw then tries to access sound card using OSS audio system and default OSS audio device name ('/dev/audio'), unless user specifies other audio device with option -d or --device.
If opening soundcard through OSS fails, cw tries to access the sound card using ALSA audio system, and default ALSA audio device name ('default'), unless user specifies other audio device with option -d or --device.
If opening soundcard through ALSA also fails, cw tries to access system console buzzer using default buzzer device '/dev/console', unless user specifies other audio device with option -d or --device.
It is very common that in order to access the console buzzer device user has to have root privileges. For that reason trying to open console buzzer almost always fails. This is not a program's bug, this is a result of operating system's restrictions. Making cw an suid binary bypasses this restriction. The program does not fork() or exec(), so making it suid should be relatively safe. Note however that this practice is discouraged for security reasons.
As stated, user can tell cw which device to use, using -d or --device option. Which device files are suitable will depend on which operating system is running, which system user ID runs cw, and which user groups user belongs to.
Despite the fact that this manual page constantly and consistently refers to Morse code elements as dots and dashes, DO NOT think in these terms when trying to learn Morse code. Always think of them as 'dit's and 'dah's.
The Morse code table in the cw(7,LOCAL) man page is provided for reference only. If learning for the first time, you will be much better off learning by hearing the characters sent, rather than by looking at the table.
Other programs running in the system may interfere with the timing of the Morse code that cw is sending. If this is a problem, either try to run on a quiescent system, or try running cw with nice(1L,C,1). UNIX is not really designed for user-level programs to do the sort of fine timing required to send Morse code. cw is therefore more sensitive than most programs to other system activity.
cw uses system itimers for its internal timing. On most UNIX flavors, itimers are not guaranteed to signal a program exactly at the specified time, and they generally offer a resolution only as good as the normal system 'clock tick' resolution. An itimer SIGALRM usually falls on a system clock tick, making it accurate to no better than 10mS on a typical 100Hz kernel.
The effect of this is that an itimer period is generally either exactly as specified, or, more likely, slightly longer. At higher WPM settings, the cumulative effect of this affects timing accuracy, because at higher speeds, there are fewer 10mS clock ticks in a dot period. For example, at 12 WPM, the dot length is 100mS, enough to contain five kernel clock ticks. But at 60 WPM, the dot length is 20mS, or just two kernel clock ticks. So at higher speeds, the effect of itimer resolutions becomes more pronounced.
To test itimer timing, first try
and note the elapsed time, which should be very close to one minute. Next, try
The elapsed time should be the same. If it has increased, this is the effect of system itimers delaying for slightly longer than the specified period (higher WPM rates make more itimer calls). That's itimers for you, not perfect for this job, but the best there is without writing some, and perhaps a lot of, kernel code.
Except for zero, which is silent, tone values lower than 10Hz may not sound at the expected pitch.
Send a string of characters at 25 WPM, 700Hz, with no extra gaps:
Send a string at varying speeds and tones on the console speaker, specifying a system console device:
Send C-cedilla, VA, and a report of the WPM setting, with extra spacing at half volume:
Cut numbers are not provided, though they can be emulated, up to a point, by pre-filtering.
An output to an optional external device, for example, keying a line on the parallel port, or a serial line, might also be useful.
Man pages for cw(7,LOCAL), libcw(3,LOCAL), cwgen(1,LOCAL), cwcp(1,LOCAL), and xcwcp(1,LOCAL).
CW Tutor Package | cw ver. 3.5.1 |