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GMX-TRJCAT(1)			     GROMACS			   GMX-TRJCAT(1)

NAME
     gmx-trjcat - Concatenate trajectory files

SYNOPSIS
	gmx trjcat [-f [<.xtc/.trr/...> [...]]] [-n [<.ndx>]] [-demux [<.xvg>]]
		   [-o [<.xtc/.trr/...> [...]]] [-tu <enum>] [-xvg <enum>]
		   [-b <time>] [-e <time>] [-dt <time>] [-[no]settime]
		   [-[no]sort] [-[no]keeplast] [-[no]overwrite] [-[no]cat]

DESCRIPTION
     gmx trjcat concatenates several input trajectory files in sorted order.  In
     case  of double time frames the one in the later file is used.  By specify-
     ing -settime you will be asked for the start time of each file.  The  input
     files  are taken from the command line, such that a command like gmx trjcat
     -f *.trr -o fixed.trr should do the trick. Using -cat, you can simply paste
     several files together  without  removal  of  frames  with  identical  time
     stamps.

     One  important option is inferred when the output file is amongst the input
     files. In that case that particular file will be appended to which  implies
     you  do not need to store double the amount of data.  Obviously the file to
     append to has to be the one with lowest starting time since  one  can  only
     append at the end of a file.

     If  the -demux option is given, the N trajectories that are read, are writ-
     ten in another order as specified in the .xvg file.  The .xvg  file  should
     contain something like:

	0  0  1  2  3  4  5
	2  1  0  2  3  5  4

     The  first  number  is the time, and subsequent numbers point to trajectory
     indices.  The frames corresponding to the numbers present at the first line
     are collected into the output trajectory. If the number of  frames  in  the
     trajectory  does  not match that in the .xvg file then the program tries to
     be smart. Beware.

OPTIONS
     Options to specify input files:

     -f [<.xtc/.trr/...> [...]] (traj.xtc)
	    Trajectory: xtc trr cpt gro g96 pdb tng h5md

     -n [<.ndx>] (index.ndx) (Optional)
	    Index file

     -demux [<.xvg>] (remd.xvg) (Optional)
	    xvgr/xmgr file

     Options to specify output files:

     -o [<.xtc/.trr/...> [...]] (trajout.xtc)
	    Trajectory: xtc trr gro g96 pdb tng h5md

     Other options:

     -tu <enum> (ps)
	    Unit for time values: fs, ps, ns, us, ms, s

     -xvg <enum> (xmgrace)
	    xvg plot formatting: xmgrace, xmgr, none

     -b <time> (-1)
	    First time to use (ps)

     -e <time> (-1)
	    Last time to use (ps)

     -dt <time> (0)
	    Only write frame when t MOD dt = first time (ps)

     -[no]settime (no)
	    Change starting time interactively

     -[no]sort (yes)
	    Sort trajectory files (not frames)

     -[no]keeplast (no)
	    Keep overlapping frames at end of trajectory

     -[no]overwrite (no)
	    Overwrite overlapping frames during appending

     -[no]cat (no)
	    Do not discard double time frames

SEE ALSO
     gmx(1)

     More information about GROMACS is available at <http://www.gromacs.org/>.

COPYRIGHT
     2026, GROMACS development team

2026.3				  Jun 25, 2026			   GMX-TRJCAT(1)

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