Starting Pd on the command line works differently on each platform (GNU/Linux, Mac OS X, and Windows).

GNU/Linux

Usually you would use just pd on the command line. If Pd is installed in a non-standard location, like when building from source, you have to specify the full path to the binary. For example ~/trunk/pd/bin/pd. Alternatively you can first cd to Pd's bin directory, and then start ./pd. For example, cd ~/trunk/pd/bin/ && ./pd

Mac OS X

Since Pd on Mac OS X has a different start-up procedure than the other platforms, start the GUI process: /Applications/Pd-0.41-4.app/Contents/MacOS/Pd or /Applications/Pd-extended.app/Contents/MacOS/Pd-extended. To run the pd process first, you have to have the Tcl/Tk's Wish.app installed on your computer somewhere findable, like /Applications. Then run: /Applications/Pd.app/Contents/Resources/bin/pd.

Windows

If you are using the Windows cmd.exe shell, use Windows paths: C:\Program Files\pd\bin\pd.com. You could also run C:\Program Files\pd\bin\pd.com from Start -> Run... and it will launch its own cmd.exe.

Windows/Cygwin

When using a Cygwin shell, you need to use UNIX-style paths with Cygwin's special directories for Windows drive letters: /cygdrive/c/Program\ Files/pd/bin/pd.com

Windows/MinGW/MSYS

When using a MinGW MSYS shell, you need to use UNIX-style paths with MSYS's special directories for Windows drive letters: /c/Program\ Files/pd/bin/pd.com