[gmx-users] why does trjcat take so much memory?

[chris.neale at utoronto.ca]

I have 28,000 .xtc files, each having a single frame and each 150K. If  
I run du -hs on the directory containing these .xtcs, I get 4.4 GB.  
Nevertheless, when I run trjcat -f *.xtc -o ../tot.xtc , my memory  
consumption goes over 11 GB and then I run out of available memory.

Sure, I could find a larger memory system, but why does it take >=3x  
more memory than the individual files took in disk space? Does anybody  
know any commands

This is gromacs 4.0.5 and 4.0.7 and 4.5-beta2.

Thank you,
Chris.