Since mailcap handling is primarily for displaying of resources, all fields like edit, print, compose etc. are ignored.
Note: Test commands are supported, but unfortunately, it's not possible to provide the file when running the test. So any test that requires a file will be considered failed and the handler will not be used.
Unfortunately, there are no native support for the copiousoutput field. The
field basically mean needs pager. So it is handled by appending a pipe and a
pager program to the command. The pager program will be read from the
environment variable. If this fails, test are made for common pager programs
/usr/bin/more in that order). So if you
define png2ascii as your handler for image/png and specify copiousoutput then
the executed command will be "
png2ascii |/usr/bin/less" if less is your pager
or present on your system.