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### fix print command

Syntax:

    fix ID group-ID print N string

- ID, group-ID are documented in fix command
- print = style name of this fix command
- N = print every N steps
- string = text string to print with optional variable names

Examples:

    fix extra all print 100 "Coords of marker atom = $x $y $z"

Description:

Print a text string to the screen and logfile every N steps during a simulation run. This can be used for diagnostic purposes or even as a debugging tool to monitor some quantity during a run. The text string must be a single argument, so it should be enclosed in double quotes if it is more than one word. If it contains variables it must be enclosed in double quotes to insure they are not evaluated when the input script is read, but will instead be evaluated when the string is printed.

See the variable command for a description of equal style variables which are the most useful ones to use with the fix print command, since they are evaluated afresh each timestep that the fix print line is output. Equal-style variables can calculate complex formulas involving atom and group properties, mathematical operations, other variables, etc.

Restart, fix_modify, output, run start/stop, minimize info:

No information about this fix is written to binary restart files. None of the fix_modify options are relevant to this fix. No global scalar or vector or per-atom quantities are stored by this fix for access by various output commands. No parameter of this fix can be used with the start/stop keywords of the run command. This fix is not invoked during energy minimization.

Restrictions:

If equal-style variables are used which contain thermo_style custom keywords for energy such as pe, eng, evdwl, ebond, etc, then they will only be up-to-date on timesteps where thermodynamics are computed. For example, if you output thermodynamics every 100 steps, but issue a fix print command with N = 2 that contains such a variable, the printed value will only be current on timesteps that are a multiple of 100. This is because the potential functions in LAMMPS (pairwise, bond, etc) only compute energies on timesteps when thermodynamic output is being performed.

Related commands:

variable, print

Default: none