cache command

Manage the FoBiS build artifact cache.

fobis cache <subcommand> [options]

The artifact cache stores compiled use=fobos dependencies keyed by a SHA-256 hash of (source commit | compiler | cflags | FoBiS version). When the key matches, the cached artifacts are restored instead of rebuilding.

Subcommands

fobis cache list

List all cached entries with key, compiler, size, and date.

fobis cache list

Example output:

  key            compiler          size   date
  ---            --------          ----   ----
  a1b2c3d4e5f6   gfortran-13     1234 KB 2026-04-11
  9f8e7d6c5b4a   ifort-2024      2048 KB 2026-03-22

fobis cache clean

Purge stale cache entries. Without --older-than, the entire cache directory is removed.

fobis cache clean [--older-than DAYS]

Option	Default	Description
--older-than DAYS	—	Delete only entries older than this many days; omit to wipe the full cache

fobis cache show

Show cache status for a specific dependency by name.

fobis cache show DEP_NAME

Cache location

Source	Path
Default	~/.fobis/cache/
FOBIS_CACHE_DIR env var	Overrides the default path
--cache-dir (on build or fetch)	Per-invocation override

Sharing a cache directory across projects on an NFS mount allows multiple projects on an HPC cluster to reuse compiled dependencies without rebuilding.

Cache key components

The cache key is SHA-256(source_commit | compiler | normalised_cflags | fobis_version).

• source_commit: the git HEAD SHA of the dependency repository
• compiler: the compiler executable name (e.g. gfortran-13)
• normalised_cflags: compilation flags sorted and deduplicated so -O2 -g and -g -O2 produce the same key
• fobis_version: ensures entries are invalidated after a FoBiS upgrade that changes build semantics

Disabling the cache

# Bypass cache for a single build
fobis build --no-cache
fobis fetch --no-cache

# Disable permanently via environment variable
export FOBIS_CACHE_DIR=/dev/null

Cache and reproducibility

The cache does not replace fobos.lock. A cache hit restores artifacts built from a specific locked commit; the lock file is still required to guarantee which commit was used. Use both together for fully reproducible builds.