113 lines
3.8 KiB
ReStructuredText
113 lines
3.8 KiB
ReStructuredText
.. index:: print
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print command
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=============
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Syntax
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""""""
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.. parsed-literal::
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print string keyword value
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* string = text string to print, which may contain variables
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* zero or more keyword/value pairs may be appended
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* keyword = *file* or *append* or *screen* or *universe*
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.. parsed-literal::
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*file* value = filename
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*append* value = filename
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*screen* value = *yes* or *no*
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*universe* value = *yes* or *no*
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Examples
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""""""""
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.. code-block:: LAMMPS
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print "Done with equilibration" file info.dat
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print Vol=$v append info.dat screen no
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print "The system volume is now $v"
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print 'The system volume is now $v'
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print "NEB calculation 1 complete" screen no universe yes
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print """
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System volume = $v
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System temperature = $t
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"""
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Description
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"""""""""""
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Print a text string to the screen and logfile. The text string must
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be a single argument, so if it is one line but more than one word, it
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should be enclosed in single or double quotes. To generate multiple
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lines of output, the string can be enclosed in triple quotes, as in
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the last example above. If the text string contains variables, they
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will be evaluated and their current values printed.
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.. versionadded:: 15Jun2023
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support for vector style variables
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See the :doc:`variable <variable>` command for a description of
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*equal* and *vector* style variables which are typically the most
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useful ones to use with the print command. Equal- and vector-style
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variables can calculate formulas involving mathematical operations,
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atom properties, group properties, thermodynamic properties, global
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values calculated by a :doc:`compute <compute>` or :doc:`fix <fix>`,
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or references to other :doc:`variables <variable>`. Vector-style
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variables are printed in a bracketed, comma-separated format,
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e.g. [1,2,3,4] or [12.5,2,4.6,10.1].
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.. note::
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As discussed on the :doc:`Commands parse <Commands_parse>` doc
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page, the text string can use "immediate" variables, specified as
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$(formula) with parenthesis, where the numeric formula has the same
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syntax as equal-style variables described on the :doc:`variable
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<variable>` doc page. This is a convenient way to evaluate a
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formula immediately without using the variable command to define a
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named variable and then use that variable in the text string. The
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formula can include a trailing colon and format string which
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determines the precision with which the numeric value is output.
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This is also explained on the :doc:`Commands parse
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<Commands_parse>` doc page.
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If you want the print command to be executed multiple times (with
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changing variable values), there are 3 options. First, consider using
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the :doc:`fix print <fix_print>` command, which will print a string
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periodically during a simulation. Second, the print command can be
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used as an argument to the *every* option of the :doc:`run <run>`
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command. Third, the print command could appear in a section of the
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input script that is looped over (see the :doc:`jump <jump>` and
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:doc:`next <next>` commands).
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If the *file* or *append* keyword is used, a filename is specified to
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which the output will be written. If *file* is used, then the
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filename is overwritten if it already exists. If *append* is used,
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then the filename is appended to if it already exists, or created if
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it does not exist.
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If the *screen* keyword is used, output to the screen and logfile can
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be turned on or off as desired.
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If the *universe* keyword is used, output to the global screen and
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logfile can be turned on or off as desired. In multi-partition
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calculations, the *screen* option and the corresponding output only
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apply to the screen and logfile of the individual partition.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`fix print <fix_print>`, :doc:`variable <variable>`
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Default
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"""""""
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The option defaults are no file output, screen = yes, and universe = no.
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