FLUSH
This is part of the generic module

This command instructs plumed to flush all the open files with a user specified frequency. Notice that all files are flushed anyway every 10000 steps.

This is useful for preventing data loss that would otherwise arise as a consequence of the code storing data for printing in the buffers. Notice that wherever it is written in the plumed input file, it will flush all the open files.

Compulsory keywords
STRIDE the frequency with which all the open files should be flushed
Examples

A command like this in the input will instruct plumed to flush all the output files every 100 steps

d1: DISTANCE ATOMS=1,10
PRINT ARG=d1 STRIDE=5 FILE=colvar1

FLUSH STRIDE=100

d2: DISTANCE ATOMS=2,11
# also this print is flushed every 100 steps:
PRINT ARG=d2 STRIDE=10 FILE=colvar2

(see also DISTANCE and PRINT).