# Environment Variables¶

The following lists environment variables that can effect the way MESA runs.

## Essential¶

### MESA_DIR¶

Location of the mesa source code.

### MESA_INLIST¶

By default MESA will look for a file called “inlist” in the local working directory for its configuration. This overrides the filename and can point to a file somewhere else.

## Misc¶

Useful things that are not environment variables.

### Command line arguments¶

./star can accept one argument that overrides the location of the inlist file (see mesa_inlist). This will also override the environment variable mesa_inlist.

./star some_other_inlist_file


### MESA_ERROR_BACKTRACE_DISABLE¶

If set disables the generation of backtraces when we call mesa_error() this is mostly helpful on macs as they don’t generate useful backtraces.

### MESA_FPE_CHECKS_ON¶

When set to 1 this will turn on a series of compile time checks as well as certain inlist options designed to catch floating point exceptions. This should not be set during a normal run.