4.8.3. LAMMPS Input Base Class

class LAMMPS_NS::Input : protected Pointers

Class for processing commands and input files.

The Input class contains methods for reading, pre-processing and parsing LAMMPS commands and input files and will dispatch commands to the respective class instances or contains the code to execute the commands directly. It also contains the instance of the Variable class which performs computations and text substitutions.

Public Functions

Input(class LAMMPS*, int, char**)

Input class constructor

This sets up the input processing, processes the -var and -echo command line flags, holds the factory of commands and creates and initializes an instance of the Variable class.

To execute a command, a specific class instance, derived from Command, is created, then its command() member function executed, and finally the class instance is deleted.

  • lmp – pointer to the base LAMMPS class

  • argc – number of entries in argv

  • argv – argument vector

void file()

Process all input from the ``FILE *`` pointer *infile*

This will read lines from infile, parse and execute them until the end of the file is reached. The infile pointer will usually point to stdin or the input file given with the -in command line flag.

void file(const char*)

Process all input from the file *filename*

This function opens the file at the path filename, put the current file pointer stored in infile on a stack and instead assign infile with the newly opened file pointer. Then it will call the Input::file() function to read, parse and execute the contents of that file. When the end of the file is reached, it is closed and the previous file pointer from the infile file pointer stack restored to infile.


filename – name of file with LAMMPS commands

char *one(const std::string&)

Process a single command from a string in *single*

This function takes the text in single, makes a copy, parses that, executes the command and returns the name of the command (without the arguments). If there was no command in single it will return nullptr.


single – string with LAMMPS command


string with name of the parsed command w/o arguments