4 .. TODO in future patch: update for accuracy, organize better, improve formatting
6 Summary of file formats
7 ^^^^^^^^^^^^^^^^^^^^^^^
13 run parameters, input for :ref:`gmx grompp` and :ref:`gmx convert-tpr`
16 input for :ref:`gmx xpm2ps`
18 .. _gmx-structure-files:
28 brookhaven Protein DataBank format
29 **Structure+mass(db):** :ref:`tpr`, :ref:`gro`, :ref:`g96`, or :ref:`pdb`
30 Structure and mass input for analysis tools.
31 When gro or pdb is used approximate masses will be read from the mass database.
37 system topology (ascii)
39 include topology (ascii)
41 residue topology (ascii)
49 system topology, parameters, coordinates and velocities (binary, portable)
55 Any kind of data (compressed, portable, any precision)
57 x, v and f (binary, full precision, portable)
59 x only (compressed, portable, any precision)
61 x and v (ascii, any precision)
63 x only (ascii, fixed high precision)
65 x only (ascii, reduced precision)
66 **Formats for full-precision data:**
67 :ref:`tng` or :ref:`trr`
68 **Generic trajectory formats:**
69 :ref:`tng`, :ref:`xtc`, :ref:`trr`, :ref:`gro`, :ref:`g96`, or :ref:`pdb`
75 energies, temperature, pressure, box size, density and virials (binary)
77 energies, temperature, pressure, box size, density and virials (binary, portable)
78 **Generic energy formats:**
79 :ref:`edr` or :ref:`ene`
85 generic, preferred for input
87 essential dynamics constraints input for :ref:`gmx mdrun`
89 Encapsulated Postscript
93 colormap input for :ref:`gmx do_dssp`
97 generic, preferred for output
101 ascii matrix data, use :ref:`gmx xpm2ps` to convert to :ref:`eps`
113 The cpt file extension stands for portable checkpoint file.
114 The complete state of the simulation is stored in the checkpoint file,
115 including extended thermostat/barostat variables, random number states
116 and NMR time averaged data.
117 With domain decomposition also the some decomposition setup information
120 See also :ref:`gmx mdrun`.
127 Files with the dat file extension contain generic input or output.
128 As it is not possible
129 to categorize all data file formats, |Gromacs| has a generic file format called
130 dat of which no format is given.
137 The dlg file format is used as input for the :ref:`gmx view`
138 trajectory viewer. These files are not meant to be altered by the end user.
147 group "Bond Options" 1 1 16 9 {
148 radiobuttons { " Thin Bonds" " Fat Bonds" " Very Fat Bonds" " Spheres" }
149 "bonds" "Ok" " F" "help bonds"
152 group "Other Options" 18 1 20 13 {
153 checkbox " Show Hydrogens" "" "" "FALSE" "help opts"
154 checkbox " Draw plus for atoms" "" "" "TRUE" "help opts"
155 checkbox " Show Box" "" "" "TRUE" "help opts"
156 checkbox " Remove PBC" "" "" "FALSE" "help opts"
157 checkbox " Depth Cueing" "" "" "TRUE" "help opts"
158 edittext "Skip frames: " "" "" "0" "help opts"
162 defbutton "Ok" "Ok" "Ok" "Ok" "help bonds"
172 Files with the edi file extension contain information for :ref:`gmx mdrun`
173 to run Molecular Dynamics with Essential Dynamics constraints.
174 It used to be possible to generate those through the options
175 provided in the `WHAT IF <http://swift.cmbi.ru.nl/whatif/>`_ program.
177 .. WEDSAM and ESSDYN seem to have vanished from WhatIf and the web
178 These files can be generated by the program <tt>WEDSAM</tt> which uses
179 output from the programs in the <tt>ESSDYN</tt> menu of the
180 <A HREF="http://www.sander.embl-heidelberg.de/whatif/">WHAT IF</A> program.
187 The edr file extension stands for portable energy file.
188 The energies are stored using the xdr protocol.
190 See also :ref:`gmx energy`.
197 The ene file extension stands for binary energy file. It holds the
198 energies as generated during your :ref:`gmx mdrun`.
200 The file can be transformed to a portable energy file (portable
201 across hardware platforms), the :ref:`edr` file using the program
204 See also :ref:`gmx energy`.
211 The eps file format is not a special |Gromacs| format, but just a
212 variant of the standard PostScript(tm). A sample eps file as
213 generated by the :ref:`gmx xpm2ps` program is
214 included below. It shows the secondary structure of a peptide as a function
217 .. image:: plotje.gif
225 A file with the g96 extension can be a GROMOS-96 initial/final
226 configuration file or a coordinate trajectory file or a combination of both.
227 The file is fixed format, all floats are written as 15.9 (files can get huge).
228 |Gromacs| supports the following data blocks in the given order:
232 - ``TITLE`` (mandatory)
236 - ``TIMESTEP`` (optional)
237 - ``POSITION/POSITIONRED`` (mandatory)
238 - ``VELOCITY/VELOCITYRED`` (optional)
241 See the GROMOS-96 manual for a complete description of the blocks.
243 Note that all |Gromacs| programs can read compressed or g-zipped files.
250 Files with the gro file extension contain a molecular structure in
251 Gromos87 format. gro files can be used as trajectory by simply
252 concatenating files. An attempt will be made to read a time value from
253 the title string in each frame, which should be preceded by
254 '``t=``', as in the sample below.
256 A sample piece is included below::
258 MD of 2 waters, t= 0.0
260 1WATER OW1 1 0.126 1.624 1.679 0.1227 -0.0580 0.0434
261 1WATER HW2 2 0.190 1.661 1.747 0.8085 0.3191 -0.7791
262 1WATER HW3 3 0.177 1.568 1.613 -0.9045 -2.6469 1.3180
263 2WATER OW1 4 1.275 0.053 0.622 0.2519 0.3140 -0.1734
264 2WATER HW2 5 1.337 0.002 0.680 -1.0641 -1.1349 0.0257
265 2WATER HW3 6 1.326 0.120 0.568 1.9427 -0.8216 -0.0244
266 1.82060 1.82060 1.82060
268 Lines contain the following information (top to bottom):
270 * title string (free format string, optional time in ps after '``t=``')
271 * number of atoms (free format integer)
272 * one line for each atom (fixed format, see below)
273 * box vectors (free format, space separated reals), values:
274 v1(x) v2(y) v3(z) v1(y) v1(z) v2(x) v2(z) v3(x) v3(y),
275 the last 6 values may be omitted (they will be set to zero).
276 |Gromacs| only supports boxes with v1(y)=v1(z)=v2(z)=0.
278 This format is fixed, ie. all columns are in a fixed
279 position. Optionally (for now only yet with trjconv) you can write gro
280 files with any number of decimal places, the format will then be
281 ``n+5`` positions with ``n`` decimal places (``n+1``
282 for velocities) in stead of ``8`` with ``3`` (with
283 ``4`` for velocities). Upon reading, the precision will be
284 inferred from the distance between the decimal points (which will be
285 ``n+5``). Columns contain the following information (from left to
288 * residue number (5 positions, integer)
289 * residue name (5 characters)
290 * atom name (5 characters)
291 * atom number (5 positions, integer)
292 * position (in nm, x y z in 3 columns, each 8 positions with 3 decimal places)
293 * velocity (in nm/ps (or km/s), x y z in 3 columns, each 8 positions with 4 decimal places)
295 Note that separate molecules or ions (e.g. water or Cl-) are regarded
296 as residues. If you want to write such a file in your own program
297 without using the |Gromacs| libraries you can use the following formats:
300 ``"%5d%-5s%5s%5d%8.3f%8.3f%8.3f%8.4f%8.4f%8.4f"``
302 ``(i5,2a5,i5,3f8.3,3f8.4)``
304 This is left as an exercise for the user
306 Note that this is the format for writing, as in the above example
307 fields may be written without spaces, and therefore can not be read
308 with the same format statement in C.
315 The hdb file extension stands for hydrogen database
316 Such a file is needed by :ref:`gmx pdb2gmx`
317 when building hydrogen atoms that were either originally missing, or that
318 were removed with ``-ignh``.
325 The itp file extension stands for include topology. These files are included in
326 topology files (with the :ref:`top` extension).
333 Logfiles are generated by some |Gromacs| programs and are usually in
334 human-readable format. Use ``more logfile``.
341 The m2p file format contains input options for the
342 :ref:`gmx xpm2ps` program. All of these options
343 are very easy to comprehend when you look at the PosScript(tm) output
344 from :ref:`gmx xpm2ps`.
348 ; Command line options of xpm2ps override the parameters in this file
349 black&white = no ; Obsolete
350 titlefont = Times-Roman ; A PostScript Font
351 titlefontsize = 20 ; Font size (pt)
352 legend = yes ; Show the legend
353 legendfont = Times-Roman ; A PostScript Font
354 legendlabel = ; Used when there is none in the .xpm
355 legend2label = ; Used when merging two xpm's
356 legendfontsize = 14 ; Font size (pt)
357 xbox = 2.0 ; x-size of a matrix element
358 ybox = 2.0 ; y-size of a matrix element
359 matrixspacing = 20.0 ; Space between 2 matrices
360 xoffset = 0.0 ; Between matrix and bounding box
361 yoffset = 0.0 ; Between matrix and bounding box
362 x-major = 20 ; Major ticks on x axis every .. frames
363 x-minor = 5 ; Id. Minor ticks
364 x-firstmajor = 0 ; First frame for major tick
365 x-majorat0 = no ; Major tick at first frame
366 x-majorticklen = 8.0 ; x-majorticklength
367 x-minorticklen = 4.0 ; x-minorticklength
368 x-label = ; Used when there is none in the .xpm
369 x-fontsize = 16 ; Font size (pt)
370 x-font = Times-Roman ; A PostScript Font
371 x-tickfontsize = 10 ; Font size (pt)
372 x-tickfont = Helvetica ; A PostScript Font
383 y-tickfont = Helvetica
390 This file maps matrix data to RGB values which is used by the
391 :ref:`gmx do_dssp` program.
393 The format of this file is as follow: first line number of elements
394 in the colormap. Then for each line: The first character is
395 a code for the secondary structure type.
396 Then comes a string for use in the legend of the plot and then the
397 R (red) G (green) and B (blue) values.
399 In this case the colors are
400 (in order of appearance): white, red, black, cyan, yellow, blue, magenta, orange.
406 E B-Sheet 1.0 0.0 0.0
407 B B-Bridge 0.0 0.0 0.0
410 H A-Helix 0.0 0.0 1.0
411 G 3-Helix 1.0 0.0 1.0
412 I 5-Helix 1.0 0.6 0.0
419 See the user guide for a detailed description of the options.
421 Below is a sample mdp file.
422 The ordering of the items is not important, but if you enter the same
423 thing twice, the **last** is used (:ref:`gmx grompp` gives you a note when
424 overriding values). Dashes and underscores on the left hand side are ignored.
426 The values of the options are values for a 1 nanosecond
427 MD run of a protein in a box of water.
429 **Note:** The parameters chosen (*e.g.,* short-range cutoffs) depend on the
430 force field being used.
440 nstxout-compressed = 5000
443 constraints = all-bonds
444 constraint-algorithm = lincs
446 cutoff-scheme = Verlet
456 tc-grps = Protein SOL
460 pcoupl = Parrinello-Rahman
462 compressibility = 4.5e-5
465 With this input :ref:`gmx grompp` will produce a commented file with the default name
466 ``mdout.mdp``. That file will contain the above options, as well as all other
467 options not explicitly set, showing their default values.
474 Files with the mtx file extension contain a matrix.
475 The file format is identical to the :ref:`trr` format.
476 Currently this file format is only used for hessian matrices,
477 which are produced with :ref:`gmx mdrun` and read by
485 The |Gromacs| index file (usually called index.ndx) contains some
486 user definable sets of atoms. The file can be read by
487 most analysis programs, by the graphics program
489 and by the preprocessor (:ref:`gmx grompp`).
490 Most of these programs create default index groups when no index
491 file is supplied, so you only need to make an index file when you need special
494 First the group name is written between square brackets.
495 The following atom numbers may be spread out over as many lines as you like.
496 The atom numbering starts at 1.
498 An example file is here:
508 There are two groups, and total nine atoms. The first group
509 **Oxygen** has 3 elements.
510 The second group **Hydrogen** has 6 elements.
512 An index file generation tool is available:
520 Files with the out file extension contain generic output. As it is not possible
521 to categorize all data file formats, |Gromacs| has a generic file format called
522 out of which no format is given.
530 Files with the :ref:`pdb` extension are molecular
531 structure files in the protein databank file format. The protein
532 databank file format describes the positions of atoms in a molecular
533 structure. Coordinates are read from the ATOM and HETATM records,
534 until the file ends or an ENDMDL record is encountered.
535 |Gromacs| programs can read and write a simulation box in the
537 The pdb format can also be used as a trajectory format:
538 several structures, separated by ENDMDL, can be read from
539 or written to one file.
544 A pdb file should look like this::
546 ATOM 1 H1 LYS 1 14.260 6.590 34.480 1.00 0.00
547 ATOM 2 H2 LYS 1 13.760 5.000 34.340 1.00 0.00
548 ATOM 3 N LYS 1 14.090 5.850 33.800 1.00 0.00
549 ATOM 4 H3 LYS 1 14.920 5.560 33.270 1.00 0.00
558 The rtp file extension stands for residue topology.
559 Such a file is needed by :ref:`gmx pdb2gmx`
560 to make a |Gromacs| topology for a protein contained in a :ref:`pdb`
561 file. The file contains the default interaction type for the 4 bonded
562 interactions and residue entries, which consist of atoms and
563 optionally bonds, angles dihedrals and impropers.
564 Parameters can be added to bonds, angles, dihedrals and impropers,
565 these parameters override the standard parameters in the :ref:`itp` files.
566 This should only be used in special cases.
567 Instead of parameters a string can be added for each bonded interaction,
568 the string is copied to the :ref:`top` file,
569 this is used for the GROMOS96 forcefield.
571 :ref:`gmx pdb2gmx` automatically generates all angles,
572 this means that the ``[angles]`` field is only
573 useful for overriding :ref:`itp` parameters.
575 :ref:`gmx pdb2gmx` automatically generates one proper
576 dihedral for every rotatable bond, preferably on heavy atoms.
577 When the ``[dihedrals]`` field is used, no other dihedrals will
578 be generated for the bonds corresponding to the specified dihedrals.
579 It is possible to put more than one dihedral on a rotatable bond.
581 :ref:`gmx pdb2gmx` sets the number exclusions to 3, which
582 means that interactions between atoms connected by at most 3 bonds are
583 excluded. Pair interactions are generated for all pairs of atoms which are
584 separated by 3 bonds (except pairs of hydrogens).
585 When more interactions need to be excluded, or some pair interactions should
586 not be generated, an ``[exclusions]`` field can be added, followed by
587 pairs of atom names on separate lines. All non-bonded and pair interactions
588 between these atoms will be excluded.
590 A sample is included below.
594 [ bondedtypes ] ; mandatory
595 ; bonds angles dihedrals impropers
600 [ atoms ] ; mandatory
601 ; name type charge chargegroup
616 [ exclusions ] ; optional
619 [ angles ] ; optional
620 ;atom1 atom2 atom3 th0 cth
622 [ dihedrals ] ; optional
623 ;atom1 atom2 atom3 atom4 phi0 cp mult
625 [ impropers ] ; optional
626 ;atom1 atom2 atom3 atom4 q0 cq
640 We use **LaTeX** for *document* processing.
641 Although the input is not so
642 user friendly, it has some advantages over *word* processors.
644 * **LaTeX** knows a lot about formatting, probably much more than you.
645 * The input is clear, you always know what you are doing
646 * It makes anything from letters to a thesis
654 Files with the ``.tng`` file extension can contain all kinds of data
655 related to the trajectory of a simulation. For example, it might
656 contain coordinates, velocities, forces and/or energies. Various :ref:`mdp`
657 file options control which of these are written by :ref:`gmx mdrun`, whether data
658 is written with compression, and how lossy that compression can be.
659 This file is in portable binary format and can be read with :ref:`gmx dump`.
663 :ref:`gmx dump` -f traj.tng
665 or if you're not such a fast reader::
667 gmx dump -f traj.tng | less
669 You can also get a quick look in the contents of the file (number of
674 :ref:`gmx check` -f traj.tng
681 The top file extension stands for topology. It is an ascii file which is
682 read by :ref:`gmx grompp` which processes it
683 and creates a binary topology (:ref:`tpr` file).
685 A sample file is included below::
688 ; Example topology file
691 ; nbfunc comb-rule gen-pairs fudgeLJ fudgeQQ
694 ; The force field files to be included
695 #include "rt41c5.itp"
702 ; nr type resnr residu atom cgnr charge
703 1 C 1 UREA C1 1 0.683
704 2 O 1 UREA O2 1 -0.683
705 3 NT 1 UREA N3 2 -0.622
706 4 H 1 UREA H4 2 0.346
707 5 H 1 UREA H5 2 0.276
708 6 NT 1 UREA N6 3 -0.622
709 7 H 1 UREA H7 3 0.346
710 8 H 1 UREA H8 3 0.276
714 3 4 1 1.000000e-01 3.744680e+05
715 3 5 1 1.000000e-01 3.744680e+05
716 6 7 1 1.000000e-01 3.744680e+05
717 6 8 1 1.000000e-01 3.744680e+05
718 1 2 1 1.230000e-01 5.020800e+05
719 1 3 1 1.330000e-01 3.765600e+05
720 1 6 1 1.330000e-01 3.765600e+05
724 2 4 1 0.000000e+00 0.000000e+00
725 2 5 1 0.000000e+00 0.000000e+00
726 2 7 1 0.000000e+00 0.000000e+00
727 2 8 1 0.000000e+00 0.000000e+00
728 3 7 1 0.000000e+00 0.000000e+00
729 3 8 1 0.000000e+00 0.000000e+00
730 4 6 1 0.000000e+00 0.000000e+00
731 5 6 1 0.000000e+00 0.000000e+00
734 ; ai aj ak funct c0 c1
735 1 3 4 1 1.200000e+02 2.928800e+02
736 1 3 5 1 1.200000e+02 2.928800e+02
737 4 3 5 1 1.200000e+02 3.347200e+02
738 1 6 7 1 1.200000e+02 2.928800e+02
739 1 6 8 1 1.200000e+02 2.928800e+02
740 7 6 8 1 1.200000e+02 3.347200e+02
741 2 1 3 1 1.215000e+02 5.020800e+02
742 2 1 6 1 1.215000e+02 5.020800e+02
743 3 1 6 1 1.170000e+02 5.020800e+02
746 ; ai aj ak al funct c0 c1 c2
747 2 1 3 4 1 1.800000e+02 3.347200e+01 2.000000e+00
748 6 1 3 4 1 1.800000e+02 3.347200e+01 2.000000e+00
749 2 1 3 5 1 1.800000e+02 3.347200e+01 2.000000e+00
750 6 1 3 5 1 1.800000e+02 3.347200e+01 2.000000e+00
751 2 1 6 7 1 1.800000e+02 3.347200e+01 2.000000e+00
752 3 1 6 7 1 1.800000e+02 3.347200e+01 2.000000e+00
753 2 1 6 8 1 1.800000e+02 3.347200e+01 2.000000e+00
754 3 1 6 8 1 1.800000e+02 3.347200e+01 2.000000e+00
757 ; ai aj ak al funct c0 c1
758 3 4 5 1 2 0.000000e+00 1.673600e+02
759 6 7 8 1 2 0.000000e+00 1.673600e+02
760 1 3 6 2 2 0.000000e+00 1.673600e+02
762 ; Include SPC water topology
777 The tpr file extension stands for portable binary run input file. This file
778 contains the starting structure of your simulation, the molecular topology
779 and all the simulation parameters. Because this file is in binary format it
780 cannot be read with a normal editor. To read a portable binary run input
785 :ref:`gmx dump` -s topol.tpr
787 or if you're not such a fast reader::
789 gmx dump -s topol.tpr | less
791 You can also compare two tpr files using:
795 :ref:`gmx check` -s1 top1 -s2 top2 | less
802 Files with the trr file extension contain the trajectory of a simulation.
803 In this file all the coordinates, velocities, forces and energies are
804 printed as you told |Gromacs| in your mdp file. This file is in portable binary
805 format and can be read with :ref:`gmx dump`::
809 or if you're not such a fast reader::
811 gmx dump -f traj.trr | less
813 You can also get a quick look in the contents of the file (number of
818 % :ref:`gmx check` -f traj.trr
825 The |Gromacs| xpm file format is compatible with the XPixMap format
826 and is used for storing matrix data.
827 Thus |Gromacs| xpm files can be viewed directly with programs like XV.
828 Alternatively, they can be imported into GIMP and scaled to 300 DPI,
829 using strong antialiasing for font and graphics.
830 The first matrix data line in an xpm file corresponds to the last matrix
832 In addition to the XPixMap format, |Gromacs| xpm files may contain
833 extra fields. The information in these fields is used when converting
834 an xpm file to EPS with :ref:`gmx xpm2ps`.
835 The optional extra field are:
837 * Before the ``gv_xpm`` declaration: ``title``, ``legend``,
838 ``x-label``, ``y-label`` and ``type``, all followed by a string.
839 The ``legend`` field determines the legend title.
840 The ``type`` field must be followed by ``"continuous"`` or
841 ``"discrete"``, this determines which type of legend will be drawn in an EPS
842 file, the default type is continuous.
843 * The xpm colormap entries may be followed by a string, which is a label for
845 * Between the colormap and the matrix data, the fields ``x-axis`` and/or
846 ``y-axis`` may be present followed by the tick-marks for that axis.
848 The example |Gromacs| xpm file below contains all the extra fields.
849 The C-comment delimiters and the colon in the extra fields are optional.
854 /* This matrix is generated by g_rms. */
855 /* title: "Backbone RMSD matrix" */
856 /* legend: "RMSD (nm)" */
857 /* x-label: "Time (ps)" */
858 /* y-label: "Time (ps)" */
859 /* type: "Continuous" */
860 static char * gv_xpm[] = {
862 "A c #FFFFFF " /* "0" */,
863 "B c #CCCCCC " /* "0.0399" */,
864 "C c #999999 " /* "0.0798" */,
865 "D c #666666 " /* "0.12" */,
866 "E c #333333 " /* "0.16" */,
867 "F c #000000 " /* "0.2" */,
868 /* x-axis: 0 40 80 120 160 200 240 280 320 360 400 440 480 */
869 /* y-axis: 0 40 80 120 160 200 240 280 320 360 400 440 480 */
889 The xtc format is a **portable** format for trajectories.
890 It uses the *xdr* routines for writing and reading
891 data which was created for the Unix NFS system. The trajectories
892 are written using a reduced precision algorithm which works
893 in the following way: the coordinates (in nm) are multiplied by a scale
894 factor, typically 1000, so that you have coordinates in pm.
895 These are rounded to integer values. Then several other tricks are
896 performed, for instance making use of the fact that atoms close
897 in sequence are usually close in space too (e.g. a water molecule).
898 To this end, the *xdr* library is extended with a special routine
899 to write 3-D float coordinates. The routine was originally written
900 by Frans van Hoesel as part of an Europort project. An updated
901 version of it can be obtained through `this link <https://github.com/Pappulab/xdrf>`_.
903 All the data is stored using calls to *xdr* routines.
906 A magic number, for the current file version its value is 1995.
908 The number of atoms in the trajectory.
914 The computational box which is stored as a set of three basis
915 vectors, to allow for triclinic PBC. For a rectangular box the
916 box edges are stored on the diagonal of the matrix.
917 **3dfcoord** x[natoms]
918 The coordinates themselves stored in reduced precision.
919 Please note that when the number of atoms is smaller than 9
920 no reduced precision is used.
922 Using xtc in your "C" programs
923 ++++++++++++++++++++++++++++++
925 To read and write these files the following "C" routines are available::
927 /* All functions return 1 if successful, 0 otherwise */
929 extern int open_xtc(XDR *xd,char *filename,char *mode);
930 /* Open a file for xdr I/O */
932 extern void close_xtc(XDR *xd);
933 /* Close the file for xdr I/O */
935 extern int read_first_xtc(XDR *xd,char *filename,
936 int *natoms,int *step,real *time,
937 matrix box,rvec **x,real *prec);
938 /* Open xtc file, read xtc file first time, allocate memory for x */
940 extern int read_next_xtc(XDR *xd,
941 int *natoms,int *step,real *time,
942 matrix box,rvec *x,real *prec);
943 /* Read subsequent frames */
945 extern int write_xtc(XDR *xd,
946 int natoms,int step,real time,
947 matrix box,rvec *x,real prec);
948 /* Write a frame to xtc file */
950 To use the library function include ``"gromacs/fileio/xtcio.h"``
951 in your file and link with ``-lgmx.$(CPU)``.
953 Using xtc in your FORTRAN programs
954 ++++++++++++++++++++++++++++++++++
956 To read and write these in a FORTRAN program use the calls to
957 ``readxtc`` and ``writextc`` as in the following sample program
958 which reads and xtc file and copies it to a new one::
962 parameter (maxatom=10000,maxx=3*maxatom)
963 integer xd,xd2,natoms,step,ret,i
964 real time,box(9),x(maxx)
966 call xdrfopen(xd,"test.xtc","r",ret)
967 print *,'opened test.xtc, ret=',ret
968 call xdrfopen(xd2,"testout.xtc","w",ret)
969 print *,'opened testout.xtc, ret=',ret
971 call readxtc(xd,natoms,step,time,box,x,prec,ret)
973 if ( ret .eq. 1 ) then
974 call writextc(xd2,natoms,step,time,box,x,prec,ret)
976 print *,'Error reading xtc'
982 To link your program use ``-L$(GMXHOME)/lib/$(CPU) -lxtcf``
983 on your linker command line.
990 Almost all output from |Gromacs| analysis tools is ready as input for
991 Grace, formerly known as Xmgr. We use Grace, because it is very flexible, and it is also
992 free software. It produces PostScript(tm) output, which is very suitable
993 for inclusion in eg. LaTeX documents, but also for other word processors.
995 A sample Grace session with |Gromacs| data is shown below:
998 :alt: Sample xvg graphic produced using the |Gromacs| tools