From 15f9987c328fd9f200af85d0e8d2b0aad991a82f Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Tue, 6 Oct 2020 18:39:22 -0400
Subject: [PATCH] add custom commands "cd" and "pwd" to the LAMMPS shell

---
 doc/src/Tools.rst                   |  7 +++++++
 tools/lammps-shell/README           | 12 +++++++-----
 tools/lammps-shell/lammps-shell.cpp | 13 +++++++++++++
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/doc/src/Tools.rst b/doc/src/Tools.rst
index 483c77038e..f29103e7af 100644
--- a/doc/src/Tools.rst
+++ b/doc/src/Tools.rst
@@ -498,9 +498,16 @@ 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
+   pwd            print current working directory
+   cd <directory> change current working directory (same as pwd if no directory)
    \|<command>     execute <command> as a shell command and return to the command prompt
    exit           exit the LAMMPS shell cleanly (unlike the "quit" command)
 
+Please note that some known shell operations are implemented in the
+LAMMPS :doc:`shell command <shell>` in a platform neutral fashion,
+while using the '\|' character will always pass the following text
+to the operating system's shell command.
+
 Compilation
 ===========
 
diff --git a/tools/lammps-shell/README b/tools/lammps-shell/README
index efa19236ce..f72305536d 100644
--- a/tools/lammps-shell/README
+++ b/tools/lammps-shell/README
@@ -84,11 +84,13 @@ 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)
+- help (or ?)    print a brief help message
+- history        display the current command history list
+- clear_history  wipe out the current command history list
+- pwd            print current working directory
+- cd <directory> change current working directory (same as pwd if no directory)
+- |<command>     execute <command> as a shell command and return to the command prompt
+- exit           exit the LAMMPS shell cleanly (unlike the "quit" command)
 
 Compilation
 ===========
diff --git a/tools/lammps-shell/lammps-shell.cpp b/tools/lammps-shell/lammps-shell.cpp
index c1f8182535..f286137e53 100644
--- a/tools/lammps-shell/lammps-shell.cpp
+++ b/tools/lammps-shell/lammps-shell.cpp
@@ -25,6 +25,7 @@
 #include <io.h>
 #include <windows.h>
 #define isatty(x) _isatty(x)
+#define getcwd(buf, len) _getcwd(buf, len)
 #endif
 
 #if !defined(_WIN32)
@@ -460,6 +461,8 @@ static void init_commands()
     // store LAMMPS shell specific command names
     commands.push_back("help");
     commands.push_back("exit");
+    commands.push_back("pwd");
+    commands.push_back("cd");
     commands.push_back("history");
     commands.push_back("clear_history");
 
@@ -549,6 +552,16 @@ static int shell_cmd(const std::string &cmd)
     } else if (words[0] == "exit") {
         free(text);
         return shell_end();
+    } else if ((words[0] == "pwd") || ((words[0] == "cd") && (words.size() == 1))) {
+        if (getcwd(buf, buflen)) std::cout << buf << "\n";
+        free(text);
+        return 0;
+    } else if (words[0] == "cd") {
+        std::string shellcmd = "shell ";
+        shellcmd += text;
+        lammps_command(lmp, shellcmd.c_str());
+        free(text);
+        return 0;
     } else if (words[0] == "history") {
         free(text);
         HIST_ENTRY **list = history_list();