add readme and makefile for LAMMPS shell

tools/lammps-shell/.gitignore

@@ -0,0 +1 @@
+/lammps-shell

tools/lammps-shell/Makefile

@@ -0,0 +1,14 @@
+SHELL=/bin/sh
+
+CXX=g++
+CXXFLAGS=-O -g -Wall -I../../src -DLAMMPS_LIB_NO_MPI
+LDFLAGS= -L../../src -llammps -lreadline
+
+lammps-shell: lammps-shell.o
+	$(CXX) -o $@ $^ $(LDFLAGS)
+
+lammps-shell.o: lammps-shell.cpp
+	$(CXX) -c $(CXXFLAGS) -o $@ $<
+
+clean:
+	@rm -f lammps-shell lammps-shell.o core *~ .lammps-history

tools/lammps-shell/README

@@ -0,0 +1,108 @@
+The LAMMPS Shell. An enhanced LAMMPS executable for interactive sessions.
+
+Overview
+========
+
+This is a program that functions very similar to the regular LAMMPS
+executable but has several modifications and additions that make it
+more powerful for interactive sessions, i.e. where you type LAMMPS
+commands from the prompt instead of reading them from a file.
+
+- It uses the readline and history libraries to provide command line
+  editing and context aware TAB-expansion (details on that below).
+
+- When processing an input file with the '-in' or '-i' flag from the
+  command line, it does not exit at the end of that input file but
+  stops at a prompt, so that additional commands can be issued
+
+- Errors will not abort the shell but return to the prompt.
+
+- It has additional commands aimed at interactive use (details below).
+
+- Interrupting a calculation with CTRL-C will not terminate the
+  session but rather enforce a timeout to cleanly stop an ongoing
+  run (more info on timeouts is in the timer command documentation).
+
+These enhancements makes the LAMMPS shell an attractive choice for
+interactive LAMMPS sessions in graphical user interfaces.
+
+TAB-expansion
+=============
+
+When writing commands interactively at the shell prompt, you can hit
+the TAB key at any time to try and complete the text.  This completion
+is context aware and will expand any first word only to commands
+available in that executable.
+
+- For style commands it will expand to available styles of the
+  corresponding categrory (e.g. pair styles after a pair_style command).
+
+- For "compute", "fix", or "dump" it will also expand only to already
+  defined groups for the group-ID keyword.
+
+- For commands like "compute_modify", "fix_modify", or "dump_modify"
+  it will expand to known compute/fix/dump IDs only.
+
+- When typing references to computes, fixes, or variables with a
+  "c_", "f_", or "v_" prefix, respectively, then the expansion will
+  to known compute/fix IDs and variable names. Variable name expansion
+  is also available for the ${name} variable syntax.
+
+- In all other cases, expansion will be 
+
+For all other
+
+Command line editing and history
+================================
+
+When typing commands, command line editing similar to what BASH
+provides is available.  Thus it is possible to move around the
+currently line and perform various cut and insert and edit operations.
+Previous commands can be retrieved by scrolling up (and down)
+or searching (e.g. with CTRL-r).
+
+Also history expansion through using the exclamation mark '!'
+can be performed.  Examples: '!!' will be replaced with the previous
+command, '!-2' will repeat the command before that, '!30' will be
+replaced with event number 30 in the command history list, and
+'!run' with the last command line that started with "run".  Adding
+a ":p" to such a history expansion will result that the expansion is
+printed and added to the history list, but NOT executed.
+On exit the LAMMPS shell will write the history list to a file
+".lammps_history" in the current working directory.  If such a
+file exists when the LAMMPS shell is launched it will be read to
+populate the history list.
+
+This is realized via the readline library and can thus be customised
+with an .inputrc file in the home directory.  For application specific
+customizations, the LAMMPS shell uses the name "lammps-shell".
+For more information about using and customizing an application using
+readline, please see the available documentation at:
+http://www.gnu.org/s/readline/#Documentation
+
+Additional commands
+===================
+
+The followind commands are added to the LAMMPS shell on top of the
+regular LAMMPS commands:
+
+- help (or ?)   print a brief help message
+- history       display the current command history list
+- clear_history wipe out the current command history list
+- |<command>    execute <command> as a shell command and return to the command prompt
+- exit          exit the LAMMPS shell cleanly (unlike the "quit" command)
+
+Compilation
+===========
+
+Compilation of the LAMMPS shell can be enabled by setting the
+CMake variable LAMMPS_SHELL to on or using the makefile in the
+tools/lammps-shell folder to compile after building LAMMPS using
+the conventional make procedure.  The makefile will likely need
+customization depending on the features and settings used for
+compiling LAMMPS.
+
+Limitations
+===========
+
+The LAMMPS shell was not designed for use with MPI parallelization.