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Some of the key parts of mcron are implemented as modules so they can be incorporated into other Guile programs, or even into C-sourced programs if they are linked against libguile.
It may be, for example, that a program needs to perform house-keeping functions at certain times of the day, in which case it can spawn (either fork or thread) a sub-process which uses a built-in mcron. Another example may be a program which must sleep until some non-absolute time specified on the Gregorian calendar (the first day of next week, for example). Finally, it may be the wish of the user to provide a program with the functionality of mcron plus a bit extra.
The base module maintains mcron’s internal job lists, and provides the main wait-run-wait loop that is mcron’s primary function. It also introduces the facilities for accumulating a set of environment modifiers, which take effect when jobs run.
| • The base module | The job list and execution loop. | |
| • The redirect module | Sending output of jobs to a mail box. | |
| • The vixie-time module | Parsing Vixie-style time specifications. | |
| • The job-specifier module | All commands for Scheme configuration files. | |
| • The vixie-specification module | Commands for reading Vixie-style crontabs. |