PetscPOpen

Runs a program on processor zero and sends either its input or output to a file.

int PetscPOpen(MPI_Comm comm,char *machine,char *program,const char mode[],FILE **fp)

Collective on MPI_Comm, but only process 0 runs the command

	comm	- MPI communicator, only processor zero runs the program
	machine	- machine to run command on or PETSC_NULL, or string with 0 in first location
	program	- name of program to run
	mode	- either r or w

fp -the file pointer where program input or output may be read or PETSC_NULL if don't care

Does not work under Windows

The program string may contain ${DISPLAY}, ${HOMEDIRECTORY} or ${WORKINGDIRECTORY}; these will be replaced with relevent values.