Gerris Manual/Object hierarchy/GfsOutput

This generic object is a GfsEvent which also defines where to write the data to output.

The syntax in parameter files is as follows:

[ GfsEvent ] FILE

where FILE is either a string defining the file in which to write the output, or a shell-script enclosed within braces to which the output will be piped. Two file names have special meaning: "stderr" and "stdout" for the standard error and standard output respectively.

If a C-like formatting string appears in the file name, it is interpreted as follows:

%d

is replaced with the current processor number.

%ld

is replaced with the current time step number.

%f

is replaced with the current physical time.

Note that most of the C language format specifiers are recognized (i.e. it is possible to use formatting strings like %05.2f etc...).

If the simulation does not start at time zero the existing files are appended otherwise they are overwritten.

The "pipe" feature of GfsOutput can for example be used to do on-the-flight post-processing of the data stream, as in the following example:

 GfsOutputPPM { istep = 1 } { ppmtoy4m -v 0 -F 24:1 | mpeg2enc -v 0 -o vorticity.mpg } { v = Vorticity }

which will convert the PPM stream generated by GfsOutputPPM directly to MPEG using the MJPEG tools collection.