Merge pull request #4266 from akohlmey/geturl-command

New geturl command to download files for LAMMPS inputs on demand

cmake/CMakeLists.txt

@@ -510,6 +510,14 @@ if(PKG_ATC OR PKG_AWPMD OR PKG_ML-QUIP OR PKG_ML-POD OR PKG_ELECTRODE OR BUILD_T
   endif()
 endif()
 
+find_package(CURL QUIET COMPONENTS HTTP HTTPS)
+option(WITH_CURL "Enable libcurl support" ${CURL_FOUND})
+if(WITH_CURL)
+  find_package(CURL REQUIRED COMPONENTS HTTP HTTPS)
+  target_compile_definitions(lammps PRIVATE -DLAMMPS_CURL)
+  target_link_libraries(lammps PRIVATE CURL::libcurl)
+endif()
+
 # tweak jpeg library names to avoid linker errors with MinGW cross-compilation
 set(JPEG_NAMES libjpeg libjpeg-62)
 find_package(JPEG QUIET)

doc/src/Build_settings.rst

@@ -8,7 +8,8 @@ explains how to do this for building both with CMake and make.
 * `FFT library`_ for use with the :doc:`kspace_style pppm <kspace_style>` command
 * `Size of LAMMPS integer types and size limits`_
 * `Read or write compressed files`_
-* `Output of JPG, PNG, and move files` via the :doc:`dump image <dump_image>` or :doc:`dump movie <dump_image>` commands
+* `Output of JPEG, PNG, and movie files`_ via the :doc:`dump image <dump_image>` or :doc:`dump movie <dump_image>` commands
+* `Support for downloading files`_
 * `Memory allocation alignment`_
 * `Workaround for long long integers`_
 * `Exception handling when using LAMMPS as a library`_ to capture errors
@@ -19,7 +20,7 @@ explains how to do this for building both with CMake and make.
 .. _cxx11:
 
 C++11 standard compliance
-------------------------------------------
+-------------------------
 
 A C++11 standard compatible compiler is a requirement for compiling LAMMPS.
 LAMMPS version 3 March 2020 is the last version compatible with the previous
@@ -31,12 +32,16 @@ flags to enable C++11 compliance.  Example for GNU c++ 4.8.x:
 
    CCFLAGS = -g -O3 -std=c++11
 
+Individual packages may require compliance with a later C++ standard
+like C++14 or C++17.  These requirements will be documented with the
+:doc:`individual packages <Packages_details>`.
+
 ----------
 
 .. _fft:
 
 FFT library
----------------------
+-----------
 
 When the KSPACE package is included in a LAMMPS build, the
 :doc:`kspace_style pppm <kspace_style>` command performs 3d FFTs which
@@ -341,8 +346,8 @@ in whichever ``lib/gpu/Makefile`` is used must be the same as above.
 
 .. _graphics:
 
-Output of JPG, PNG, and movie files
+Output of JPEG, PNG, and movie files
---------------------------------------------------
+------------------------------------
 
 The :doc:`dump image <dump_image>` command has options to output JPEG or
 PNG image files.  Likewise, the :doc:`dump movie <dump_image>` command
@@ -356,9 +361,9 @@ requires the following settings:
       .. code-block:: bash
 
          -D WITH_JPEG=value      # yes or no
-                                 # default = yes if CMake finds JPEG files, else no
+                                 # default = yes if CMake finds JPEG development files, else no
          -D WITH_PNG=value       # yes or no
-                                 # default = yes if CMake finds PNG and ZLIB files, else no
+                                 # default = yes if CMake finds PNG and ZLIB development files, else no
          -D WITH_FFMPEG=value    # yes or no
                                  # default = yes if CMake can find ffmpeg, else no
 
@@ -446,12 +451,58 @@ during a run.
    available using a compression library instead, which is what the
    :ref:`COMPRESS package <PKG-COMPRESS>` enables.
 
+--------------------------------------------------
+
+.. _libcurl:
+
+Support for downloading files
+-----------------------------
+
+.. versionadded:: TBD
+
+The :doc:`geturl command <geturl>` command uses the `the libcurl library
+<https://curl.se/libcurl/>`_ to download files.  This requires that
+LAMMPS is compiled accordingly which needs the following settings:
+
+.. tabs::
+
+   .. tab:: CMake build
+
+      .. code-block:: bash
+
+         -D WITH_CURL=value      # yes or no
+                                 # default = yes if CMake finds CURL development files, else no
+
+      Usually these settings are all that is needed.  If CMake cannot
+      find the graphics header, library, executable files, you can set
+      these variables:
+
+      .. code-block:: bash
+
+         -D CURL_INCLUDE_DIR=path    # path to folder which contains curl.h header file
+         -D CURL_LIBRARY=path        # path to libcurls.a (.so) file
+
+   .. tab:: Traditional make
+
+      .. code-block:: make
+
+         LMP_INC = -DLAMMPS_CURL  <other LMP_INC settings>
+
+         CURL_INC = -I/usr/local/include   # path to curl folder with curl.h
+         CURL_PATH = -L/usr/lib            # paths to libcurl.a(.so) if make cannot find it
+         CURL_LIB = -lcurl                 # library names
+
+      As with CMake, you do not need to set ``CURL_INC`` or ``CURL_PATH``,
+      if make can find the libcurl header and library files in their
+      default system locations.  You must specify ``CURL_LIB`` with a
+      paths or linker flags to link to libcurl.
+
 ----------
 
 .. _align:
 
 Memory allocation alignment
----------------------------------------
+---------------------------
 
 This setting enables the use of the "posix_memalign()" call instead of
 "malloc()" when LAMMPS allocates large chunks of memory.  Vector

doc/src/Commands_all.rst

@@ -54,6 +54,7 @@ table above.
    * :doc:`echo <echo>`
    * :doc:`fix <fix>`
    * :doc:`fix_modify <fix_modify>`
+   * :doc:`geturl <geturl>`
    * :doc:`group <group>`
    * :doc:`if <if>`
    * :doc:`improper_coeff <improper_coeff>`

doc/src/commands_list.rst

@@ -45,6 +45,7 @@ Commands
    fix
    fix_modify
    fitpod_command
+   geturl
    group
    group2ndx
    hyper

doc/src/geturl.rst

@@ -0,0 +1,82 @@
+.. index:: geturl
+
+geturl command
+==============
+
+Syntax
+""""""
+
+.. code-block:: LAMMPS
+
+   geturl url keyword args ...
+
+* url = URL of the file to download
+* zero or more keyword argument pairs may be provided
+* keyword = *output* or *verify* or *overwrite* or *verbose*
+
+  .. parsed-literal::
+
+     *output* filename = write to *filename* instead of inferring the name from the URL
+     *verify* yes/no = verify SSL certificate and hostname if *yes*, do not if *no*
+     *overwrite* yes/no = if *yes* overwrite the output file in case it exists, do not if *no*
+     *verbose* yes/no = if *yes* write verbose debug output from libcurl to screen, do not if *no*
+
+Examples
+""""""""
+
+.. code-block:: LAMMPS
+
+   geturl https://www.ctcms.nist.gov/potentials/Download/1990--Ackland-G-J-Vitek-V--Cu/2/Cu2.eam.fs
+   geturl https://github.com/lammps/lammps/blob/develop/bench/in.lj output in.bench-lj
+
+Description
+"""""""""""
+
+.. versionadded:: TBD
+
+Download a file from an URL to the local disk. This is implemented with
+the `libcurl library <https:://curl.se/libcurl/>`_ which supports a
+large variety of protocols including "http", "https", "ftp", "scp",
+"sftp", "file".  The transfer will only be performed on MPI rank 0.
+
+The *output* keyword can be used to set the filename. By default, the last part
+of the URL is used.
+
+The *verify* keyword determines whether ``libcurl`` will validate the
+SSL certificate and hostname for encrypted connections.  Turning this
+off may be required when using a proxy or connecting to a server with a
+self-signed SSL certificate.
+
+The *overwrite* keyword determines whether a file should be overwritten if it
+already exists.  If the argument is *no*, then the download will be skipped
+if the file exists.
+
+The *verbose* keyword determines whether a detailed protocol of the steps
+performed by libcurl is written to the screen.  Using the argument *yes*
+can be used to debug connection issues when the *geturl* command does not
+behave as expected.  If the argument is *no*, geturl will operate silently
+and only report the error status number provided by libcurl, in case of a
+failure.
+
+----------
+
+Restrictions
+""""""""""""
+
+This command is part of the EXTRA-COMMAND package.  It is only enabled
+if LAMMPS was built with that package.  See the :doc:`Build package
+<Build_package>` page for more info.  It also requires that LAMMPS was
+built with support for `the libcurl library
+<https://curl.se/libcurl/>`_.  See the page about :ref:`Compiling LAMMPS
+with libcurl support <libcurl>` for further info.  If support for
+libcurl is not included, using *geturl* will trigger an error.
+
+Related commands
+""""""""""""""""
+
+:doc:`shell <shell>`
+
+Default
+"""""""
+
+*verify* = yes, *overwrite* = yes

doc/utils/sphinx-config/false_positives.txt

@@ -1298,6 +1298,7 @@ Gershgorin
 getrusage
 getter
 gettimeofday
+geturl
 gewald
 Gezelter
 Gflop
@@ -1492,6 +1493,8 @@ hplanck
 Hs
 hstyle
 html
+http
+https
 hTST
 https
 hu
@@ -3349,6 +3352,7 @@ Schunk
 Schuring
 Schwen
 Sci
+scp
 screenshot
 screenshots
 Scripps
@@ -3389,6 +3393,7 @@ setvel
 sevenbody
 sfftw
 sfree
+sftp
 Sg
 sgcmc
 Shan
@@ -3903,6 +3908,7 @@ upenn
 upto
 Urbakh
 Urbana
+url
 UreyBradley
 Usabiaga
 usec

examples/COUPLE/plugin/liblammpsplugin.c

@@ -150,6 +150,7 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(config_has_png_support);
   ADDSYM(config_has_jpeg_support);
   ADDSYM(config_has_ffmpeg_support);
+  ADDSYM(config_has_curl_support);
   ADDSYM(config_has_exceptions);
 
   ADDSYM(config_has_package);

examples/COUPLE/plugin/liblammpsplugin.h

@@ -203,6 +203,7 @@ struct _liblammpsplugin {
   int (*config_has_png_support)();
   int (*config_has_jpeg_support)();
   int (*config_has_ffmpeg_support)();
+  int (*config_has_curl_support)();
   int (*config_has_exceptions)();
 
   int (*config_has_package)(const char *);

fortran/lammps.f90

@@ -196,6 +196,7 @@ MODULE LIBLAMMPS
     PROCEDURE, NOPASS :: config_has_jpeg_support => lmp_config_has_jpeg_support
     PROCEDURE, NOPASS :: config_has_ffmpeg_support &
                                         => lmp_config_has_ffmpeg_support
+    PROCEDURE, NOPASS :: config_has_curl_support => lmp_config_has_curl_support
     PROCEDURE, NOPASS :: config_has_exceptions => lmp_config_has_exceptions
     PROCEDURE, NOPASS :: config_has_package => lmp_config_has_package
     PROCEDURE, NOPASS :: config_package_count => lammps_config_package_count
@@ -793,6 +794,12 @@ MODULE LIBLAMMPS
       INTEGER(c_int) :: lammps_config_has_ffmpeg_support
     END FUNCTION lammps_config_has_ffmpeg_support
 
+    FUNCTION lammps_config_has_curl_support() BIND(C)
+      IMPORT :: c_int
+      IMPLICIT NONE
+      INTEGER(c_int) :: lammps_config_has_curl_support
+    END FUNCTION lammps_config_has_curl_support
+
     FUNCTION lammps_config_has_exceptions() BIND(C)
       IMPORT :: c_int
       IMPLICIT NONE
@@ -2881,6 +2888,14 @@ CONTAINS
     lmp_config_has_ffmpeg_support = (has_ffmpeg_support /= 0_c_int)
   END FUNCTION lmp_config_has_ffmpeg_support
 
+  ! equivalent function to lammps_config_has_curl_support
+  LOGICAL FUNCTION lmp_config_has_curl_support()
+    INTEGER(c_int) :: has_curl_support
+
+    has_curl_support = lammps_config_has_curl_support()
+    lmp_config_has_curl_support = (has_curl_support /= 0_c_int)
+  END FUNCTION lmp_config_has_curl_support
+
   ! equivalent function to lammps_config_has_exceptions
   LOGICAL FUNCTION lmp_config_has_exceptions()
     INTEGER(c_int) :: has_exceptions

python/lammps/core.py

@@ -1969,6 +1969,21 @@ class lammps(object):
 
   # -------------------------------------------------------------------------
 
+  @property
+  def has_curl_support(self):
+    """ Report whether the LAMMPS shared library was compiled with support
+    for downloading files through libcurl.
+
+    This is a wrapper around the :cpp:func:`lammps_config_has_curl_support`
+    function of the library interface.
+
+    :return: state of CURL support
+    :rtype: bool
+    """
+    return self.lib.lammps_config_has_curl_support() != 0
+
+  # -------------------------------------------------------------------------
+
   def has_package(self, name):
     """ Report if the named package has been enabled in the LAMMPS shared library.
 

src/.gitignore

@@ -1075,6 +1075,8 @@
 /fix_wall_srd.h
 /fix_widom.cpp
 /fix_widom.h
+/geturl.cpp
+/geturl.h
 /gpu_extra.h
 /group_ndx.cpp
 /group_ndx.h

src/EXTRA-COMMAND/geturl.cpp

@@ -0,0 +1,119 @@
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   LAMMPS development team: developers@lammps.org
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing authors:  Axel Kohlmeyer (Temple U),
+------------------------------------------------------------------------- */
+
+#include "geturl.h"
+
+#include "comm.h"
+#include "error.h"
+
+#if defined(LAMMPS_CURL)
+#include <curl/curl.h>
+#endif
+
+using namespace LAMMPS_NS;
+
+/* ---------------------------------------------------------------------- */
+
+void GetURL::command(int narg, char **arg)
+{
+#if !defined(LAMMPS_CURL)
+  error->all(FLERR, "LAMMPS has not been compiled with libcurl support");
+#else
+  if (narg < 1) utils::missing_cmd_args(FLERR, "geturl", error);
+  int verify = 1;
+  int overwrite = 1;
+  int verbose = 0;
+
+  // process arguments
+
+  std::string url = arg[0];
+
+  // sanity check
+
+  if ((url.find(':') == std::string::npos) || (url.find('/') == std::string::npos))
+    error->all(FLERR, "URL '{}' is not a supported URL", url);
+
+  std::string output = url.substr(url.find_last_of('/') + 1);
+  if (output.empty()) error->all(FLERR, "URL '{}' must end in a file string", url);
+
+  int iarg = 1;
+  while (iarg < narg) {
+    if (strcmp(arg[iarg], "output") == 0) {
+      if (iarg + 2 > narg) utils::missing_cmd_args(FLERR, "geturl output", error);
+      output = arg[iarg + 1];
+      ++iarg;
+    } else if (strcmp(arg[iarg], "overwrite") == 0) {
+      if (iarg + 2 > narg) utils::missing_cmd_args(FLERR, "geturl overwrite", error);
+      overwrite = utils::logical(FLERR, arg[iarg + 1], false, lmp);
+      ++iarg;
+    } else if (strcmp(arg[iarg], "verify") == 0) {
+      if (iarg + 2 > narg) utils::missing_cmd_args(FLERR, "geturl verify", error);
+      verify = utils::logical(FLERR, arg[iarg + 1], false, lmp);
+      ++iarg;
+    } else if (strcmp(arg[iarg], "verbose") == 0) {
+      if (iarg + 2 > narg) utils::missing_cmd_args(FLERR, "geturl verbose", error);
+      verbose = utils::logical(FLERR, arg[iarg + 1], false, lmp);
+      ++iarg;
+    } else {
+      error->all(FLERR, "Unknown geturl keyword: {}", arg[iarg]);
+    }
+    ++iarg;
+  }
+
+  // only download files from rank 0
+
+  if (comm->me != 0) return;
+
+  if (!overwrite && platform::file_is_readable(output)) return;
+
+  // open output file for writing
+
+  FILE *out = fopen(output.c_str(), "wb");
+  if (!out)
+    error->all(FLERR, "Cannot open output file {} for writing: {}", output, utils::getsyserror());
+
+  // initialize curl and perform download
+
+  CURL *curl;
+  curl_global_init(CURL_GLOBAL_DEFAULT);
+  curl = curl_easy_init();
+  if (curl) {
+    curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
+    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *) out);
+    curl_easy_setopt(curl, CURLOPT_FILETIME, 1L);
+    curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1L);
+    if (verbose && screen) {
+      curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
+      curl_easy_setopt(curl, CURLOPT_STDERR, (void *) screen);
+    }
+    if (!verify) {
+      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
+      curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
+    }
+    auto res = curl_easy_perform(curl);
+    if (res != CURLE_OK) {
+      long response = 0L;
+      curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &response);
+      error->one(FLERR, "Download of {} failed with: {} {}", output, curl_easy_strerror(res),
+                 response);
+    }
+    curl_easy_cleanup(curl);
+  }
+  curl_global_cleanup();
+  fclose(out);
+#endif
+}

src/EXTRA-COMMAND/geturl.h

@@ -0,0 +1,34 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   LAMMPS development team: developers@lammps.org
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+#ifdef COMMAND_CLASS
+// clang-format off
+CommandStyle(geturl,GetURL);
+// clang-format on
+#else
+
+#ifndef LMP_GETURL_H
+#define LMP_GETURL_H
+
+#include "command.h"
+
+namespace LAMMPS_NS {
+
+class GetURL : public Command {
+ public:
+  GetURL(class LAMMPS *lmp) : Command(lmp) {};
+  void command(int, char **) override;
+};
+}    // namespace LAMMPS_NS
+#endif
+#endif

src/MAKE/Makefile.mpi

@@ -35,9 +35,9 @@ LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX98
 # MPI wrapper compiler/linker can provide this info
 # can point to dummy MPI library in src/STUBS as in Makefile.serial
 # use -D MPICH and OMPI settings in INC to avoid C++ lib conflicts
-# INC = path for mpi.h, MPI compiler settings
+# MPI_INC = path for mpi.h, MPI compiler settings
-# PATH = path for MPI library
+# MPI_PATH = path for MPI library
-# LIB = name of MPI library
+# MPI_LIB = name of MPI library
 
 MPI_INC =       -DMPICH_SKIP_MPICXX -DOMPI_SKIP_MPICXX=1
 MPI_PATH =
@@ -46,9 +46,9 @@ MPI_LIB =
 # FFT library
 # see discussion in Section 3.5.2 of manual
 # can be left blank to use provided KISS FFT library
-# INC = -DFFT setting, e.g. -DFFT_FFTW, FFT compiler settings
+# FFT_INC = -DFFT setting, e.g. -DFFT_FFTW, FFT compiler settings
-# PATH = path for FFT library
+# FFT_PATH = path for FFT library
-# LIB = name of FFT library
+# FFT_LIB = name of FFT library
 
 FFT_INC =
 FFT_PATH =
@@ -57,14 +57,25 @@ FFT_LIB =
 # JPEG and/or PNG library
 # see discussion in Section 3.5.4 of manual
 # only needed if -DLAMMPS_JPEG or -DLAMMPS_PNG listed with LMP_INC
-# INC = path(s) for jpeglib.h and/or png.h
+# JPG_INC = path(s) for jpeglib.h and/or png.h
-# PATH = path(s) for JPEG library and/or PNG library
+# JPG_PATH = path(s) for JPEG library and/or PNG library
-# LIB = name(s) of JPEG library and/or PNG library
+# JPG_LIB = name(s) of JPEG library and/or PNG library
 
 JPG_INC =
 JPG_PATH =
 JPG_LIB =
 
+# CURL library
+# see discussion in Section 3.5.6 of manual
+# only needed if -DLAMMPS_CURL listed with LMP_INC
+# CURL_INC = path(s) for curl/curl.h
+# CURL_PATH = path(s) for CURL library
+# CURL_LIB = name(s) of CURL library, e.g. -lcurl
+
+CURL_INC =
+CURL_PATH =
+CURL_LIB =
+
 # library for loading shared objects (defaults to -ldl, should be empty on Windows)
 # uncomment to change the default
 
@@ -77,9 +88,9 @@ JPG_LIB =
 include Makefile.package.settings
 include Makefile.package
 
-EXTRA_INC = $(LMP_INC) $(PKG_INC) $(MPI_INC) $(FFT_INC) $(JPG_INC) $(PKG_SYSINC)
+EXTRA_INC = $(LMP_INC) $(PKG_INC) $(MPI_INC) $(FFT_INC) $(JPG_INC) $(CURL_INC) $(PKG_SYSINC)
-EXTRA_PATH = $(PKG_PATH) $(MPI_PATH) $(FFT_PATH) $(JPG_PATH) $(PKG_SYSPATH)
+EXTRA_PATH = $(PKG_PATH) $(MPI_PATH) $(FFT_PATH) $(JPG_PATH) $(CURL_PATH) $(PKG_SYSPATH)
-EXTRA_LIB = $(PKG_LIB) $(MPI_LIB) $(FFT_LIB) $(JPG_LIB) $(PKG_SYSLIB) $(DYN_LIB)
+EXTRA_LIB = $(PKG_LIB) $(MPI_LIB) $(FFT_LIB) $(JPG_LIB) $(CURL_LIB) $(PKG_SYSLIB) $(DYN_LIB)
 EXTRA_CPP_DEPENDS = $(PKG_CPP_DEPENDS)
 EXTRA_LINK_DEPENDS = $(PKG_LINK_DEPENDS)
 

src/MAKE/Makefile.serial

@@ -35,9 +35,9 @@ LMP_INC =	-DLAMMPS_GZIP -DLAMMPS_MEMALIGN=64  # -DLAMMPS_CXX98
 # MPI wrapper compiler/linker can provide this info
 # can point to dummy MPI library in src/STUBS as in Makefile.serial
 # use -D MPICH and OMPI settings in INC to avoid C++ lib conflicts
-# INC = path for mpi.h, MPI compiler settings
+# MPI_INC = path for mpi.h, MPI compiler settings
-# PATH = path for MPI library
+# MPI_PATH = path for MPI library
-# LIB = name of MPI library
+# MPI_LIB = name of MPI library
 
 MPI_INC =       -I../STUBS
 MPI_PATH =      -L../STUBS
@@ -46,9 +46,9 @@ MPI_LIB =	-lmpi_stubs
 # FFT library
 # see discussion in Section 3.5.2 of manual
 # can be left blank to use provided KISS FFT library
-# INC = -DFFT setting, e.g. -DFFT_FFTW, FFT compiler settings
+# FFT_INC = -DFFT setting, e.g. -DFFT_FFTW, FFT compiler settings
-# PATH = path for FFT library
+# FFT_PATH = path for FFT library
-# LIB = name of FFT library
+# FFT_LIB = name of FFT library
 
 FFT_INC =
 FFT_PATH =
@@ -57,14 +57,25 @@ FFT_LIB =
 # JPEG and/or PNG library
 # see discussion in Section 3.5.4 of manual
 # only needed if -DLAMMPS_JPEG or -DLAMMPS_PNG listed with LMP_INC
-# INC = path(s) for jpeglib.h and/or png.h
+# JPG_INC = path(s) for jpeglib.h and/or png.h
-# PATH = path(s) for JPEG library and/or PNG library
+# JPG_PATH = path(s) for JPEG library and/or PNG library
-# LIB = name(s) of JPEG library and/or PNG library
+# JPG_LIB = name(s) of JPEG library and/or PNG library
 
 JPG_INC =
 JPG_PATH =
 JPG_LIB =
 
+# CURL library
+# see discussion in Section 3.5.6 of manual
+# only needed if -DLAMMPS_CURL listed with LMP_INC
+# CURL_INC = path(s) for curl/curl.h
+# CURL_PATH = path(s) for CURL library
+# CURL_LIB = name(s) of CURL library, e.g. -lcurl
+
+CURL_INC =
+CURL_PATH =
+CURL_LIB =
+
 # library for loading shared objects (defaults to -ldl, should be empty on Windows)
 # uncomment to change the default
 
@@ -77,9 +88,9 @@ JPG_LIB =
 include Makefile.package.settings
 include Makefile.package
 
-EXTRA_INC = $(LMP_INC) $(PKG_INC) $(MPI_INC) $(FFT_INC) $(JPG_INC) $(PKG_SYSINC)
+EXTRA_INC = $(LMP_INC) $(PKG_INC) $(MPI_INC) $(FFT_INC) $(JPG_INC) $(CURL_INC) $(PKG_SYSINC)
-EXTRA_PATH = $(PKG_PATH) $(MPI_PATH) $(FFT_PATH) $(JPG_PATH) $(PKG_SYSPATH)
+EXTRA_PATH = $(PKG_PATH) $(MPI_PATH) $(FFT_PATH) $(JPG_PATH) $(CURL_PATH) $(PKG_SYSPATH)
-EXTRA_LIB = $(PKG_LIB) $(MPI_LIB) $(FFT_LIB) $(JPG_LIB) $(PKG_SYSLIB) $(DYN_LIB)
+EXTRA_LIB = $(PKG_LIB) $(MPI_LIB) $(FFT_LIB) $(JPG_LIB) $(CURL_LIB) $(PKG_SYSLIB) $(DYN_LIB)
 EXTRA_CPP_DEPENDS = $(PKG_CPP_DEPENDS)
 EXTRA_LINK_DEPENDS = $(PKG_LINK_DEPENDS)
 

src/info.cpp

@@ -296,6 +296,7 @@ void Info::command(int narg, char **arg)
     if (has_png_support()) fputs("-DLAMMPS_PNG\n",out);
     if (has_jpeg_support()) fputs("-DLAMMPS_JPEG\n",out);
     if (has_ffmpeg_support()) fputs("-DLAMMPS_FFMPEG\n",out);
+    if (has_curl_support()) fputs("-DLAMMPS_CURL\n",out);
     if (has_fft_single_support()) fputs("-DFFT_SINGLE\n",out);
 
 #if defined(LAMMPS_BIGBIG)
@@ -857,6 +858,8 @@ bool Info::is_available(const char *category, const char *name)
       return has_jpeg_support();
     } else if (strcmp(name,"ffmpeg") == 0) {
       return has_ffmpeg_support();
+    } else if (strcmp(name,"curl") == 0) {
+      return has_curl_support();
     } else if (strcmp(name,"fft_single") == 0) {
       return has_fft_single_support();
     } else if (strcmp(name,"exceptions") == 0) {
@@ -1077,6 +1080,14 @@ bool Info::has_ffmpeg_support() {
 #endif
 }
 
+bool Info::has_curl_support() {
+#ifdef LAMMPS_CURL
+  return true;
+#else
+  return false;
+#endif
+}
+
 bool Info::has_fft_single_support() {
 #ifdef FFT_SINGLE
   return true;

src/info.h

@@ -28,7 +28,7 @@ namespace LAMMPS_NS {
 
 class Info : public Command {
  public:
-  Info(class LAMMPS *lmp) : Command(lmp){};
+  Info(class LAMMPS *lmp) : Command(lmp) {};
   void command(int, char **) override;
 
   bool is_active(const char *, const char *);
@@ -42,6 +42,7 @@ class Info : public Command {
   static bool has_png_support();
   static bool has_jpeg_support();
   static bool has_ffmpeg_support();
+  static bool has_curl_support();
   static bool has_fft_single_support();
   static bool has_exceptions();
   static bool has_package(const std::string &);

src/lammps.cpp

@@ -1454,6 +1454,7 @@ void LAMMPS::print_config(FILE *fp)
   if (Info::has_png_support()) fputs("-DLAMMPS_PNG\n",fp);
   if (Info::has_jpeg_support()) fputs("-DLAMMPS_JPEG\n",fp);
   if (Info::has_ffmpeg_support()) fputs("-DLAMMPS_FFMPEG\n",fp);
+  if (Info::has_curl_support()) fputs("-DLAMMPS_CURL\n",fp);
   if (Info::has_fft_single_support()) fputs("-DFFT_SINGLE\n",fp);
 #if defined(LAMMPS_BIGBIG)
   fputs("-DLAMMPS_BIGBIG\n",fp);

src/library.cpp

@@ -5877,6 +5877,26 @@ int lammps_config_has_ffmpeg_support() {
 
 /* ---------------------------------------------------------------------- */
 
+/** Check if the LAMMPS library supports downloading files via libcurl
+
+\verbatim embed:rst
+
+.. versionadded::TBD
+
+The LAMMPS :doc:`geturl command <geturl>` supports downloading files
+through using `the libcurl library <https://curl.se/libcurl/>`_.
+This function checks whether this feature was :ref:`enabled at compile
+time <libcurl>` and LAMMPS linked to the libcurl library.
+\endverbatim
+ *
+ * \return 1 if yes, otherwise 0
+ */
+int lammps_config_has_curl_support() {
+  return Info::has_curl_support() ? 1 : 0;
+}
+
+/* ---------------------------------------------------------------------- */
+
 /** Check whether LAMMPS errors will throw C++ exceptions.
  *
 \verbatim embed:rst

src/library.h

@@ -243,6 +243,7 @@ int lammps_config_has_gzip_support();
 int lammps_config_has_png_support();
 int lammps_config_has_jpeg_support();
 int lammps_config_has_ffmpeg_support();
+int lammps_config_has_curl_support();
 int lammps_config_has_exceptions();
 
 int lammps_config_has_package(const char *);

tools/lammps-gui/highlighter.cpp

@@ -23,7 +23,7 @@ Highlighter::Highlighter(QTextDocument *parent) :
                              "thermo|print|thermo_style|"
                              "timer|pair_write|bond_write|angle_write|dihedral_write)\\s+(\\S+)")),
     isOutput2(QStringLiteral("^\\s*(write_dump|shell|thermo_modify)\\s+(\\S+)\\s+(\\S+)")),
-    isRead(QStringLiteral("^\\s*(include|read_restart|read_data|read_dump|molecule)")),
+    isRead(QStringLiteral("^\\s*(include|read_restart|read_data|read_dump|molecule|geturl)\\s+(\\S+)")),
     isStyle(QStringLiteral("^\\s*(fix|compute|dump)\\s+(\\S+)\\s+(\\S+)\\s+(\\S+)")),
     isForce(QStringLiteral(
         "^\\s*(pair_style|bond_style|angle_style|dihedral_style|improper_style|kspace_style|pair_"

tools/swig/lammps.i

@@ -171,6 +171,7 @@ extern int    lammps_config_has_gzip_support();
 extern int    lammps_config_has_png_support();
 extern int    lammps_config_has_jpeg_support();
 extern int    lammps_config_has_ffmpeg_support();
+extern int    lammps_config_has_curl_support();
 extern int    lammps_config_has_exceptions();
 extern int    lammps_config_has_package(const char *);
 extern int    lammps_config_package_count();
@@ -359,6 +360,7 @@ extern int    lammps_config_has_gzip_support();
 extern int    lammps_config_has_png_support();
 extern int    lammps_config_has_jpeg_support();
 extern int    lammps_config_has_ffmpeg_support();
+extern int    lammps_config_has_curl_support();
 extern int    lammps_config_has_exceptions();
 extern int    lammps_config_has_package(const char *);
 extern int    lammps_config_package_count();

unittest/commands/test_simple_commands.cpp

@@ -19,6 +19,7 @@
 #include "info.h"
 #include "input.h"
 #include "output.h"
+#include "platform.h"
 #include "update.h"
 #include "utils.h"
 #include "variable.h"
@@ -214,9 +215,9 @@ TEST_F(SimpleCommandsTest, Quit)
     TEST_FAILURE(".*ERROR: Expected integer .*", command("quit xxx"););
 
     // the following tests must be skipped with OpenMPI or MPICH 4.1 and later due to using threads
-    if (platform::mpi_vendor() == "Open MPI") GTEST_SKIP();
+    if (platform::mpi_vendor() == "Open MPI") GTEST_SKIP() << "OpenMPI";
 #if defined(MPICH_NUMVERSION)
-    if (MPICH_NUMVERSION >= 40100000) GTEST_SKIP();
+    if (MPICH_NUMVERSION >= 40100000) GTEST_SKIP() << "MPICH with threads";
 #endif
     ASSERT_EXIT(command("quit"), ExitedWithCode(0), "");
     ASSERT_EXIT(command("quit 9"), ExitedWithCode(9), "");
@@ -412,7 +413,7 @@ TEST_F(SimpleCommandsTest, Plugin)
 {
     const char *bindir = getenv("LAMMPS_PLUGIN_BIN_DIR");
     const char *config = getenv("CMAKE_CONFIG_TYPE");
-    if (!bindir) GTEST_SKIP();
+    if (!bindir) GTEST_SKIP() << "LAMMPS_PLUGIN_BIN_DIR not set";
     std::string loadfmt = platform::path_join("plugin load ", bindir);
     if (config) loadfmt = platform::path_join(loadfmt, config);
     loadfmt = platform::path_join(loadfmt, "{}plugin.so");
@@ -556,6 +557,50 @@ TEST_F(SimpleCommandsTest, CiteMe)
     // no new citation. no CITE-CITE-CITE- lines
     ASSERT_THAT(text, Not(ContainsRegex(".*CITE-CITE-CITE-CITE.*")));
 }
+
+TEST_F(SimpleCommandsTest, Geturl)
+{
+    if (!LAMMPS::is_installed_pkg("EXTRA-COMMAND")) GTEST_SKIP();
+    platform::unlink("index.html");
+    platform::unlink("myindex.html");
+    if (Info::has_curl_support()) {
+        BEGIN_CAPTURE_OUTPUT();
+        command("geturl https://www.lammps.org/index.html");
+        command("geturl https://www.lammps.org/index.html output myindex.html");
+        END_CAPTURE_OUTPUT();
+        EXPECT_TRUE(platform::file_is_readable("index.html"));
+        EXPECT_TRUE(platform::file_is_readable("myindex.html"));
+        FILE *fp = fopen("index.html", "wb");
+        fputs("just testing\n", fp);
+        fclose(fp);
+        BEGIN_CAPTURE_OUTPUT();
+        command("geturl https://www.lammps.org/index.html overwrite no");
+        END_CAPTURE_OUTPUT();
+        char checkme[20];
+        fp = fopen("index.html", "rb");
+        fgets(checkme, 19, fp);
+        fclose(fp);
+        EXPECT_EQ(strcmp(checkme, "just testing\n"), 0);
+        BEGIN_CAPTURE_OUTPUT();
+        command("geturl https://www.lammps.org/index.html overwrite yes");
+        END_CAPTURE_OUTPUT();
+        fp = fopen("index.html", "rb");
+        fgets(checkme, 19, fp);
+        fclose(fp);
+        EXPECT_NE(strcmp(checkme, "just testing\n"), 0);
+        TEST_FAILURE(".*ERROR: Illegal geturl command: missing argument.*", command("geturl "););
+        TEST_FAILURE(".*ERROR: URL 'dummy' is not a supported URL.*", command("geturl dummy"););
+        TEST_FAILURE(".*ERROR on proc 0: Download of xxx.txt failed with: "
+                     "HTTP response code said error 404.*",
+                     command("geturl https://www.lammps.org/xxx.txt"););
+    } else {
+        TEST_FAILURE(".*ERROR: LAMMPS has not been compiled with libcurl support*",
+                     command("geturl https:://www.lammps.org/index.html"););
+    }
+    platform::unlink("index.html");
+    platform::unlink("myindex.html");
+}
+
 } // namespace LAMMPS_NS
 
 int main(int argc, char **argv)