l0b0 / cronlist Goto Github PK

It would be nice to print lines like

at '2000-01-01 00:00:00' <<< 'updatedb'

to be able to duplicate the command at arbitrary times easily.

Possibly by reimplementing in Rust

The C implementation checks each cron entry for a match for every minute. The following algorithm should be more efficient:

1. Find the next run time for every entry. For C entries this should be O(C), but could be quite tricky to work out.
2. Print whichever one of them is the earliest; O(C) again.
3. Get the next run time for the entry which was just printed. O(1)
4. Repeat from 2 until a stop condition is met.

With a fixed number N of entries to print, C cron entries and M minutes between now and the Nth cron run, this algorithm should be O(N+C).

Should remember to return iterators rather than lists where applicable, so that it can process everything asynchronously.

Feature progress:

• Parse time field entries
  • Numbers like 1
  • Ranges like 1-3 = 1,2,3
  • Steps like 1-5/2 = 1,3,5
  • First through last like *
  • Month and day of week names like Nov = 11, Mon = 1, Sun = 0 (not 7!)
  • Special values like day of week 7 = 0
  • Nicknames like @monthly
• Parse commands
  • Trivial commands like command
  • Whitespace in commands
  • Trailing whitespace in commands
  • Preceding whitespace in commands
• Parse whole crontab entry
  • Normal entries
  • Ignore empty lines
  • Ignore comments
  • Warn in case of other unparseable entries
• Parse multiple crontab entries
• Calculate next run time for an entry
• Get the next entry to run
• Get the next N entries to run, --entries
• Read crontab from standard input
• --help
• --from, --to

Non-functional requirements:

• Get to 100% and verify it on every commit.
• Format the code and verify compliance
• Read and follow Rust API guidelines
• Calculate and limit cyclomatic complexity and possibly other metrics

Once these are done, the following should probably be separate tickets:

• Command line parameter to accept entries with username (i.e., either three or seven fields). Should probably result in printing the username column.
• By default get an infinite stream of future cron jobs. This is more useful than printing just the next run, and forces the program to be stream based.
• Handle undocumented nicknames like @midnight. Are these documented outside of man 5 crontab, or do I have to read the source?
• Only put the Entry.command in Run
• impl fmt::Display for Run instead of printing its properties.
• Return Self from fn new
• Change linting preferences:
  • Set up blacklisted_name to contain "data".
  • Set cyclomatic-complexity-threshold to maybe 2 or 4.
  • Set single-char-binding-names-threshold to 0.
  • Set too-many-arguments-threshold to maybe 5.
  • Try disallowing maybe_infinite_iter, missing_docs_in_private_items, option_unwrap_used, print_stdout
  • Disallow cast_possible_truncation, cast_possible_wrap, cast_precision_loss, cast_sign_loss, decimal_literal_representation, else_if_without_else, empty_enum, enum_glob_use, fallible_impl_from, filter_map, float_arithmetic, float_cmp_const, if_not_else, indexing_slicing, int_plus_one, integer_arithmetic (need to read up on how to do this securely), invalid_upcast_comparisons, items_after_statements, mem_forget, mut_mut, mutex_integer, nonminimal_bool, option_map_unwrap_or, option_map_unwrap_or_else, pub_enum_variant_names, range_plus_one, replace_consts, result_map_unwrap_or_else, result_unwrap_used, shadow_reuse, shadow_same, shadow_unrelated, similar_names, single_match_else, string_add, string_add_assign, stutter, unicode_not_nfc, unseparated_literal_suffix, use_debug, use_self, used_underscore_binding, wrong_pub_self_convention

Will not be implemented, at least for now:

• Reading from specific crontab file. By default at least the program should wait for text on standard input.
• Any kind of handling of @reboot - this will have to be considered infinitely into the future.