All options can be abbreviated to their shortest unique prefix. You may use two hyphens instead of one to designate an option. You may use either white space or equals signs between an option name and its value.
To create a TGA image with transparency (i.e. with an alpha mask), use RGBA PAM input. Some Netpbm programs that generate images with alpha masks generate them in that format. For another way to create the proper input stream, see pamstack.
You may specify at most one of -mono, -cmap, and -rgb. If you specify neither, the default image type is the most highly constrained compatible type is used, where monochrome is more constrained than colormapped which is in turn more constrained than unmapped.
This program was called ppmtotga until Netpbm 10.6 (July 2002). That was always a misnomer, though, because a PPM class program would not be able to tell the difference between PGM and PPM input (it would all look like PPM), and thus could not choose the output Targa image type based on the type of the input. Netpbm 10.6 also added the ability to handle an alpha channel, to it became a PAM class program.