About FoBiS.py

FoBiS.py (Fortran Building System for poor people) is a KISS build tool for modern Fortran projects. It automatically resolves inter-module dependency hierarchies so you never have to track them manually in makefiles.

The problem it solves

Consider this project layout:

└── src
    ├── main.f90          ! program, uses nested_1
    └── nested-1
        ├── first_dep.f90 ! module nested_1, includes second_dep.inc
        └── nested-2
            └── second_dep.inc

Writing a correct Makefile for this requires knowing the full compilation order, tracking which .mod files exist and where, and updating every rule whenever the dependency graph changes. As project size grows, this becomes error-prone and tedious.

FoBiS.py parses sources on every invocation, builds the complete dependency graph, and compiles in the correct order automatically:

FoBiS.py build

That single command:

1. Recursively scans ./ for all Fortran sources
2. Parses each file for module, use, include, and program statements
3. Resolves the full dependency hierarchy
4. Compiles in the correct order, skipping up-to-date objects
5. Links all programs found

Key capabilities

• Automatic dependency resolution — parses use and include statements across the full source tree, regardless of nesting or file naming mismatches between modules and files
• Timestamp-based incremental builds — only recompiles what changed
• Multi-compiler support — GNU, Intel, AMD, IBM, NAG, PGI, NVIDIA, custom
• Parallel compilation — independent translation units compiled concurrently with -j N
• fobos configuration file — INI-style makefile replacement with modes, templates, variables, and custom rules
• Advanced auto-rebuild triggers — recompile when flags change (cflags_heritage), when libraries change (volatile libs), or when upstream projects change (dependon)
• GitHub dependency fetching — FoBiS.py fetch clones and builds external FoBiS projects declared in the fobos [dependencies] section
• Doctests — introspective micro unit tests embedded in Fortran doc comments, Python-doctest style
• GNU Makefile export — generate a standard Makefile from the resolved dependency graph

How it works

CLI args + fobos file
        │
        ▼
  FoBiSConfig      ← parses options, fobos modes, loads fetched deps
        │
        ▼
  parse_files()    ← walks src dirs, parses each .f90/.F90/... file
        │
        ▼
dependency_hiearchy()  ← resolves module/include graph, orders compilation
        │
        ▼
  Builder.build()  ← parallel compile → link

Design philosophy

FoBiS.py follows the KISS principle throughout:

• Configuration-file-free by default — FoBiS.py build works without any configuration for most projects
• INI-style fobos — when configuration is needed, the fobos file uses a simple, human-readable format with no special syntax
• Same options everywhere — fobos option names are identical to their CLI switch names; there is no separate concept to learn
• Composable — fobos modes, templates, variables, and rules compose cleanly without hidden interactions