# print command

## Syntax

    print string keyword value

-   string = text string to print, which may contain variables

-   zero or more keyword/value pairs may be appended

-   keyword = *file* or *append* or *screen* or *universe*

        *file* value = filename
        *append* value = filename
        *screen* value = *yes* or *no*
        *universe* value = *yes* or *no*

## Examples

``` LAMMPS
print "Done with equilibration" file info.dat
print Vol=$v append info.dat screen no
print "The system volume is now $v"
print 'The system volume is now $v'
print "NEB calculation 1 complete" screen no universe yes
print """
System volume = $v
System temperature = $t
"""
```

## Description

Print a text string to the screen and logfile. The text string must be a
single argument, so if it is one line but more than one word, it should
be enclosed in single or double quotes. To generate multiple lines of
output, the string can be enclosed in triple quotes, as in the last
example above. If the text string contains variables, they will be
evaluated and their current values printed.

::: versionadded
15Jun2023

support for vector style variables
:::

See the [variable](variable) command for a description of *equal* and
*vector* style variables which are typically the most useful ones to use
with the print command. Equal- and vector-style variables can calculate
formulas involving mathematical operations, atom properties, group
properties, thermodynamic properties, global values calculated by a
[compute](compute) or [fix](fix), or references to other
[variables](variable). Vector-style variables are printed in a
bracketed, comma-separated format, e.g. \[1,2,3,4\] or
\[12.5,2,4.6,10.1\].

:::: note
::: title
Note
:::

As discussed on the [Commands parse](Commands_parse) doc page, the text
string can use \"immediate\" variables, specified as \$(formula) with
parenthesis, where the numeric formula has the same syntax as
equal-style variables described on the [variable](variable) doc page.
This is a convenient way to evaluate a formula immediately without using
the variable command to define a named variable and then use that
variable in the text string. The formula can include a trailing colon
and format string which determines the precision with which the numeric
value is output. This is also explained on the [Commands
parse](Commands_parse) doc page.
::::

If you want the print command to be executed multiple times (with
changing variable values), there are 3 options. First, consider using
the [fix print](fix_print) command, which will print a string
periodically during a simulation. Second, the print command can be used
as an argument to the *every* option of the [run](run) command. Third,
the print command could appear in a section of the input script that is
looped over (see the [jump](jump) and [next](next) commands).

If the *file* or *append* keyword is used, a filename is specified to
which the output will be written. If *file* is used, then the filename
is overwritten if it already exists. If *append* is used, then the
filename is appended to if it already exists, or created if it does not
exist.

If the *screen* keyword is used, output to the screen and logfile can be
turned on or off as desired.

If the *universe* keyword is used, output to the global screen and
logfile can be turned on or off as desired. In multi-partition
calculations, the *screen* option and the corresponding output only
apply to the screen and logfile of the individual partition.

## Restrictions

> none

## Related commands

[fix print](fix_print), [variable](variable)

## Default

The option defaults are no file output, screen = yes, and universe = no.