rtprint

display data from ports

Author: Geoffrey Biggs and contributors
Date: 2011-10-24
Copyright: EPL-1.0
Version: 3.0
Manual section:1
Manual group:User commands

Synopsis

rtprint [options] <path1>:<port1> [<path2>:<port2>...]

Description

Print the data being sent by one or more output ports to stdout.

By default, only the first value received from one or more ports is printed. Options are available to print multiple values or print regularly for a specified length of time. In any one loop of the port checks, if only one port out of multiple has data available, that is counted as a print for the purposes of printing a fixed number of times.

To print data which cannot be natively printed by Python, create a formatting function to print that data. The function must receive one argument: the data to print. For example:

def rawpy(data):
    return data.__repr__()

A connection will be made to each port using the default connection settings compatible with that port.

Options

-m MODULES, --mod=MODULES
 Extra modules to import. If automatic module loading struggles with the constant's data types, try listing the modules here. The module and its __POA partner will be imported.
-n MAX, --number=MAX
 Specify the number of times to read from any ports.
-p PATHS, --path=PATHS
 Extra module search paths to add to the PYTHONPATH.
-r RATE, --rate=RATE
 Specify the rate in Hertz at which to read and print.
-t TIMEOUT, --timeout=TIMEOUT
 Read data for this many seconds, then stop. This option overrides --number.
--version Show program's version number and exit
-h, --help Show a help message and exit
-v, --verbose Output verbose information. [Default: False]

Paths

rtshell uses paths to indicate objects in the RTC Tree. A path is the address of object. Name servers and naming contexts on name servers are considered directories. Managers and RT-Components are considered 'files'. As with the POSIX cat command, the path specified as an argument to commands is appended to the current rtshell working directory, which is stored in the RTCSH_CWD environment variable and changeable using the rtcwd command.

The available paths depend on the known name servers at the time the command is executed. This is a combination of the servers listed in the RTCSH_NAMESERVERS environment variable and the servers used in given paths.

For example, /localhost/comp0.rtc refers to the component named comp0.rtc registered on the name server at localhost. /localhost/manager/comp0.rtc refers to the component comp0.rtc in the directory manager on the localhost name server. ./comp0.rtc refers to that component in the current directory.

When specifying a port on an RT-Component, it should be placed after the path, separated by a colon. For example, /localhost/comp0.rtc:data refers to the port data on the component comp0.rtc.

Some commands that create new ports accept extra options in the paths, such as a name for the automatically generated port, or a formatter. The format for specifying these paths is:

path:port.name#formatter

For example:

/localhost/blurg.host_cxt/comp0.rtc:input.stuff#a_printer

This specifies that the automatically generated port should be named stuff, and the data type it handles should be printed using the a_printer function (which must be available, usually it is provided by the user in a loadable module). The port will be connected to the input port of the comp0.rtc component.

The name component is optional. If it is not present, neither should the . character be. For example:

/localhost/blurg.host_cxt/comp0.rtc:input#a_printer

The formatter component is optional. If it is not present, neither should the # character be. For example:

/localhost/blurg.host_cxt/comp0.rtc:input.stuff

Environment

RTCTREE_ORB_ARGS
A list of arguments, separated by semi-colons, to pass to the ORB when creating it. Optional.
RTCTREE_NAMESERVERS
A list of name server addresses, separated by semi-colons, to parse when creating the RTCTree. Each server in the list will be added to the tree, making it available for browsing with rtshell. Optional.
RTSH_CWD
The current working directory in the tree. Do not set this variable; it is set automatically by rtshell.

The only variable that should normally be set by the user is RTCTREE_NAMESERVERS. Set this to a list of name server addresses, separated by semi-colons, that rtshell should interact with. For example, in a Bash shell, the following command will set the known name serves to localhost, 192.168.0.1:65346 and example.com:

$ export RTCTREE_NAMESERVERS=localhost;192.168.0.1:65346;example.com

Diagnostics

Returns zero on success and non-zero on failure.

Verbose output and error messages are printed to stderr.

Examples

$ rtprint /localhost/ConsoleIn0.rtc:out

Print the first value sent by the ConsoleIn0.rtc component over its out port.

$ rtprint /localhost/ConsoleIn0.rtc:out -n 5

Print the first five values sent by the ConsoleIn0.rtc component over its out port.

$ rtprint /localhost/ConsoleIn0.rtc:out -t 5

Print the values sent by the ConsoleIn0.rtc component over its out port for five seconds.

$ rtprint /localhost/ConsoleIn0.rtc:out -t 5 -r 10

Print the values sent by the ConsoleIn0.rtc component over its out port up to ten times a second for for five seconds.

$ rtprint /localhost/ConsoleIn0.rtc:out#rawpy

Print the first value sent by the ConsoleIn0.rtc component over its out port as a Python expression using the inbuilt rawpy formatter.

$ rtprint /localhost/ConsoleIn0.rtc:out#printers.my_formatter

Print the first value sent by the ConsoleIn0.rtc component over its out port using the my_formatter formatting function from the printers module to print the data.

See rtinject(1) for examples using --mod and --path.

See Also

rtcat (1), rtinject (1), rtlog (1)