Comtrol eCos - Manual (Page 779)

Writing New Devices - host
}
The first call checks for a flag -o13 or --o13 - the code treats options with single and double hyphens inter-
changeably. The second call checks for an argument of the form -mark= < value > or a pair of arguments -mark
< value > . The value part of a name/value pair can be obtained using synth::argv_get_value;
variable speed 1
if { [synth::argv_defined "-mark="] } {
set mark [synth::argv_get_value "-mark="]
if { ![string is integer $mark] || ($mark < 1) || ($mark > 9) } {
< issue diagnostic >
} else {
set speed $mark
}
}
synth::argv_get_value should only be used after a successful call to synth::argv_defined. At present there is no
support for some advanced forms of command line argument processing. For example it is not possible to repeat a
certain option such as
-v or --verbose , with each occurrence increasing the level of verbosity.
If a script is going to have its own set of command-line arguments then it should give appropriate details if the user
specifies
--help . This involves a hook function:
namespace eval my_device {
proc help_hook { } {
puts " -o13 : activate the omega 13 device"
puts " -mark < speed > : set speed. Valid values are 1 to 9."
}
synth::hook_add "help" my_device::help_hook
}
The Target Definition File
Most device scripts will want to check entries in the target definition file for run-time configuration information.
The Tcl procedures for this are as follows:
synth::tdf_has_device < name >
synth::tdf_get_devices
synth::tdf_has_option < devname > < option >
synth::tdf_get_option < devname > < option >
synth::tdf_get_options < devname > < option >
synth::tdf_get_all_options < devname >
synth::tdf_has_device can be used to check whether or not the target definition file had an entry
synth_device < name > . Usually the name will match the type of device, so the console.tcl script will look
for a target definition file entry console . synth::tdf_get_devices returns a list of all device entries in the target
definition file.
Once it is known that the target definition file has an entry for a certain device, it is possible to check for options
within the entry. synth::tdf_has_option just checks for the presence, returning a boolean:
if { [synth::tdf_has_option "console" "appearance"] } {
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