Command line interface

Two command_line applications are provided with msprime: msp and mspms. The msp program is an experimental interface for interacting with the library, and is a POSIX compliant command line interface. The mspms program is a fully-ms compatible interface. This is useful for those who wish to get started quickly with using the library, and also as a means of plugging msprime into existing work flows. However, there is a substantial overhead involved in translating data from msprime’s native history file into legacy formats, and so new code should use the Python API where possible.


The msp program provides a convenient interface to the msprime API. It is based on subcommands that either generate or consume a tree sequence file. The simulate subcommand runs a simulation storing the results in a file. The other commands are concerned with converting this file into other formats.


This tool is very new, and the interface may need to change over time. This should be considered an alpha feature!

msp simulate

msp simulate provides a command line interface to the msprime.simulate() API function. Using the parameters provided at the command line, we run a simulation and then save the resulting tree sequence to the file provided as an argument.


The way in which recombination and mutation rates are specified is different to ms. In ms these rates are scaled by the length of the simulated region, whereas we use rates per unit distance. The rationale for this change is to simplify running simulations on a variety of sequence lengths, so that we need to change only one parameter and not three simultaneously. See API Documentation for more on this point.


The mspms program is an ms-compatible command line interface to the msprime library. This interface should be useful for legacy applications, where it can be used as a drop-in replacement for ms. This interface is not recommended for new applications, particularly if the simulated trees are required as part of the output as Newick is very inefficient. The Python API is the recommended interface, providing direct access to the structures used within msprime.

Supported Features

mspms supports a subset of ms’s functionality. Please open an issue on GitHub if there is a feature of ms that you would like to see added. We currently support:

  • Basic functionality (sample size, replicates, tree and haplotype output);
  • Recombination (via the -r option);
  • Spatial structure with arbitrary migration matrices;
  • Support for ms demographic events. (The implementation of the -es option is limited, and has restrictions on how it may be combined with other options.)

Gene-conversion is not currently supported, but is planned for a future release.

Argument details

This section provides the detailed listing of the arguments to mspms (also available via mspms --help). See the documentation for ms for details on how these values should be interpreted.