diff --git a/doc/shell.html b/doc/shell.html
index 7953130af2..0bb8b3b6d8 100644
--- a/doc/shell.html
+++ b/doc/shell.html
@@ -15,7 +15,7 @@
 </P>
 <PRE>shell cmd args 
 </PRE>
-<UL><LI>cmd = <I>cd</I> or <I>mkdir</I> or <I>mv</I> or <I>rm</I> or <I>rmdir</I> or arbitrary command 
+<UL><LI>cmd = <I>cd</I> or <I>mkdir</I> or <I>mv</I> or <I>rm</I> or <I>rmdir</I> or <I>putenv</I> or arbitrary command 
 
 <PRE>  <I>cd</I> arg = dir
     dir = directory to change to
@@ -28,6 +28,8 @@
     file1,file2 = one or more filenames to delete
   <I>rmdir</I> args = dir1 dir2 ...
     dir1,dir2 = one or more directories to delete
+  <I>putenv</I> args = var1=value1 var2=value2
+    var=value = one of more definitions of environment variables
   anything else is passed as a command to the shell for direct execution 
 </PRE>
 
@@ -40,6 +42,7 @@ shell mkdir tmp1 tmp2 tmp3
 shell rmdir tmp1
 shell mv log.lammps hold/log.1
 shell rm TMP/file1 TMP/file2
+shell putenv LAMMPS_POTENTIALS=../../potentials
 shell my_setup file1 10 file2
 shell my_post_process 100 dump.out 
 </PRE>
@@ -77,6 +80,12 @@ files.
 more directories.  A directory must be empty to be successfully
 removed.
 </P>
+<P>The <I>putenv</I> cmd defines or updates an environment variable directly.
+Since this command does not pass through the shell, no shell variable
+expansion or globbing is performed, only the usual substitution for
+LAMMPS variables defined with the <A HREF = "variable.html">variable</A> command is
+performed.  The resulting string is then used literally.
+</P>
 <P>Any other cmd is passed as-is to the shell along with its arguments as
 one string, invoked by the C-library system() call.  For example,
 these lines in your input script:
diff --git a/doc/shell.txt b/doc/shell.txt
index 1369df80a9..205164f874 100644
--- a/doc/shell.txt
+++ b/doc/shell.txt
@@ -12,7 +12,7 @@ shell command :h3
 
 shell cmd args :pre
 
-cmd = {cd} or {mkdir} or {mv} or {rm} or {rmdir} or arbitrary command :ulb,l
+cmd = {cd} or {mkdir} or {mv} or {rm} or {rmdir} or {putenv} or arbitrary command :ulb,l
   {cd} arg = dir
     dir = directory to change to
   {mkdir} args = dir1 dir2 ...
@@ -24,6 +24,8 @@ cmd = {cd} or {mkdir} or {mv} or {rm} or {rmdir} or arbitrary command :ulb,l
     file1,file2 = one or more filenames to delete
   {rmdir} args = dir1 dir2 ...
     dir1,dir2 = one or more directories to delete
+  {putenv} args = var1=value1 var2=value2
+    var=value = one of more definitions of environment variables
   anything else is passed as a command to the shell for direct execution :pre
 :ule
 
@@ -35,6 +37,7 @@ shell mkdir tmp1 tmp2 tmp3
 shell rmdir tmp1
 shell mv log.lammps hold/log.1
 shell rm TMP/file1 TMP/file2
+shell putenv LAMMPS_POTENTIALS=../../potentials
 shell my_setup file1 10 file2
 shell my_post_process 100 dump.out :pre
 
@@ -72,6 +75,12 @@ The {rmdir} cmd executes the Unix "rmdir" command to remove one or
 more directories.  A directory must be empty to be successfully
 removed.
 
+The {putenv} cmd defines or updates an environment variable directly.
+Since this command does not pass through the shell, no shell variable
+expansion or globbing is performed, only the usual substitution for
+LAMMPS variables defined with the "variable"_variable.html command is
+performed.  The resulting string is then used literally.
+
 Any other cmd is passed as-is to the shell along with its arguments as
 one string, invoked by the C-library system() call.  For example,
 these lines in your input script:
diff --git a/doc/variable.html b/doc/variable.html
index 8ab277568c..1e11913bc3 100644
--- a/doc/variable.html
+++ b/doc/variable.html
@@ -17,7 +17,7 @@
 </PRE>
 <UL><LI>name = name of variable to define 
 
-<LI>style = <I>delete</I> or <I>index</I> or <I>loop</I> or <I>world</I> or <I>universe</I> or <I>uloop</I> or <I>string</I> or <I>file</I> or <I>atomfile</I> or <I>equal</I> or <I>atom</I> 
+<LI>style = <I>delete</I> or <I>index</I> or <I>loop</I> or <I>world</I> or <I>universe</I> or <I>uloop</I> or <I>string</I> or <I>getenv</I> or <I>file</I> or <I>atomfile</I> or <I>equal</I> or <I>atom</I> 
 
 <PRE>  <I>delete</I> = no args
   <I>index</I> args = one or more strings
@@ -39,6 +39,7 @@
     N = integer size of loop
     pad = all values will be same length, e.g. 001, 002, ..., 100
   <I>string</I> arg = one string
+  <I>getenv</I> arg = one string
   <I>file</I> arg = filename
   <I>atomfile</I> arg = filename
   <I>equal</I> or <I>atom</I> args = one formula containing numbers, thermo keywords, math operations, group functions, atom values and vectors, compute/fix/variable references
@@ -139,11 +140,11 @@ means that using the <A HREF = "Section_start.html#start_7">command-line switch<
 script.
 </P>
 <P>There are two exceptions to this rule.  First, variables of style
-<I>string</I> and <I>equal</I> and <I>atom</I> ARE redefined each time the command is
-encountered.  This allows these style of variables to be redefined
-multiple times in an input script.  In a loop, this means the formula
-associated with an <I>equal</I> or <I>atom</I> style variable can change if it
-contains a substitution for another variable, e.g. $x.
+<I>string</I>, <I>getenv</I>, <I>equal</I> and <I>atom</I> ARE redefined each time the
+command is encountered.  This allows these style of variables to be
+redefined multiple times in an input script.  In a loop, this means
+the formula associated with an <I>equal</I> or <I>atom</I> style variable can
+change if it contains a substitution for another variable, e.g. $x.
 </P>
 <P>Second, as described below, if a variable is iterated on to the end of
 its list of strings via the <A HREF = "next.html">next</A> command, it is removed
@@ -246,6 +247,16 @@ single string is that a variable with <I>string</I> style can be redefined.
 E.g. by another command later in the input script, or if the script is
 read again in a loop.
 </P>
+<P>For the <I>getenv</I> style, a single string is assigned to the variable
+which should be the name of an environment variable.  When the
+variable is evaluated, it returns the value of the environment
+variable, or an empty string if it not defined.  This style of
+variable can be used to adapt the behavior of LAMMPS input scripts via
+environment variable settings, or to retrieve information that has
+been previously stored with the <A HREF = "shell.html">shell putenv</A> command.
+Note that because environment variable settings are stored by the
+operating systems, they persist beyond a <A HREF = "clear.html">clear</A> command.
+</P>
 <P>For the <I>file</I> style, a filename is provided which contains a list of
 strings to assign to the variable, one per line.  The strings can be
 numeric values if desired.  See the discussion of the next() function
diff --git a/doc/variable.txt b/doc/variable.txt
index b81c9c84de..ad11cc0b27 100644
--- a/doc/variable.txt
+++ b/doc/variable.txt
@@ -13,7 +13,7 @@ variable command :h3
 variable name style args ... :pre
 
 name = name of variable to define :ulb,l
-style = {delete} or {index} or {loop} or {world} or {universe} or {uloop} or {string} or {file} or {atomfile} or {equal} or {atom} :l
+style = {delete} or {index} or {loop} or {world} or {universe} or {uloop} or {string} or {getenv} or {file} or {atomfile} or {equal} or {atom} :l
   {delete} = no args
   {index} args = one or more strings
   {loop} args = N
@@ -34,6 +34,7 @@ style = {delete} or {index} or {loop} or {world} or {universe} or {uloop} or {st
     N = integer size of loop
     pad = all values will be same length, e.g. 001, 002, ..., 100
   {string} arg = one string
+  {getenv} arg = one string
   {file} arg = filename
   {atomfile} arg = filename
   {equal} or {atom} args = one formula containing numbers, thermo keywords, math operations, group functions, atom values and vectors, compute/fix/variable references
@@ -133,11 +134,11 @@ means that using the "command-line switch"_Section_start.html#start_7
 script.
 
 There are two exceptions to this rule.  First, variables of style
-{string} and {equal} and {atom} ARE redefined each time the command is
-encountered.  This allows these style of variables to be redefined
-multiple times in an input script.  In a loop, this means the formula
-associated with an {equal} or {atom} style variable can change if it
-contains a substitution for another variable, e.g. $x.
+{string}, {getenv}, {equal} and {atom} ARE redefined each time the
+command is encountered.  This allows these style of variables to be
+redefined multiple times in an input script.  In a loop, this means
+the formula associated with an {equal} or {atom} style variable can
+change if it contains a substitution for another variable, e.g. $x.
 
 Second, as described below, if a variable is iterated on to the end of
 its list of strings via the "next"_next.html command, it is removed
@@ -240,6 +241,16 @@ single string is that a variable with {string} style can be redefined.
 E.g. by another command later in the input script, or if the script is
 read again in a loop.
 
+For the {getenv} style, a single string is assigned to the variable
+which should be the name of an environment variable.  When the
+variable is evaluated, it returns the value of the environment
+variable, or an empty string if it not defined.  This style of
+variable can be used to adapt the behavior of LAMMPS input scripts via
+environment variable settings, or to retrieve information that has
+been previously stored with the "shell putenv"_shell.html command.
+Note that because environment variable settings are stored by the
+operating systems, they persist beyond a "clear"_clear.html command.
+
 For the {file} style, a filename is provided which contains a list of
 strings to assign to the variable, one per line.  The strings can be
 numeric values if desired.  See the discussion of the next() function