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read_data.html 39.51 KiB 
<HTML>
<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A> 
</CENTER>






<HR>

<H3>read_data command 
</H3>
<P><B>Syntax:</B>
</P>
<PRE>read_data file keyword args ... 
</PRE>
<UL><LI>file = name of data file to read in 

<LI>zero or more keyword/arg pairs may be appended 

<LI>keyword = <I>fix</I> 

<PRE>  <I>fix</I> args = fix-ID header-string section-string
    fix-ID = ID of fix to process header lines and sections of data file
    header-string = header lines containing this string will be passed to fix
    section-string = section names with this string will be passed to fix 
</PRE>

</UL>
<P><B>Examples:</B>
</P>
<PRE>read_data data.lj
read_data ../run7/data.polymer.gz
read_data data.protein fix mycmap crossterm CMAP 
</PRE>
<P><B>Description:</B>
</P>
<P>Read in a data file containing information LAMMPS needs to run a
simulation.  The file can be ASCII text or a gzipped text file
(detected by a .gz suffix).  This is one of 3 ways to specify initial
atom coordinates; see the <A HREF = "read_restart.html">read_restart</A> and
<A HREF = "create_atoms.html">create_atoms</A> commands for alternative methods.
</P>
<P>The structure of the data file is important, though many settings and
sections are optional or can come in any order.  See the examples
directory for sample data files for different problems.
</P>
<P>A data file has a header and a body.  The header appears first.  The
first line of the header is always skipped; it typically contains a
description of the file.  Then lines are read one at a time.  Lines
can have a trailing comment starting with '#' that is ignored.  If the
line is blank (only whitespace after comment is deleted), it is
skipped.  If the line contains a header keyword, the corresponding
value(s) is read from the line.  If it doesn't contain a header
keyword, the line begins the body of the file.
</P>
<P>The body of the file contains zero or more sections.  The first line
of a section has only a keyword.  This line can have a trailing
comment starting with '#' that is either ignored or can be used to
check for a style match, as described below.  The next line is
skipped.  The remaining lines of the section contain values.  The
number of lines depends on the section keyword as described below.
Zero or more blank lines can be used between sections.  Sections can
appear in any order, with a few exceptions as noted below.
</P>
<P>The keyword <I>fix</I> can be used one or more times.  Each usage specifies
a fix that will be used to process a specific portion of the data
file.  Any header line containing <I>header-string</I> and any section with
a name containing <I>section-string</I> will be passed to the specified