day-utils

You landed a gig. Your band will play Fridays and Saturdays, now through the end of the year. You want to send these dates to the newspaper, and they insist on their strict format.

This is not at all stressful, if you have day-utils.

day-range next friday .. dec 31 | lines 7 1 2 | day-format Friday, October 31st

day-utils are principally two command line tools: day-range outputs a sequence of consecutive dates, and day-format rewrites dates in various formats.

A simple filter for lines in arithmetic progression is included.

Prerequisites

lua 5.1+ or luajit 2.0.5, the LPeg library.

Installation

Copy day-range, day-format, and, if you wish, lines, somewhere in your path, edit their first lines if necessary, and make them executable.

Usage: day-range

day-range sunday .. + 3 days

will print four dates on stdout, in YYYY-MM-DD format, of the coming Sunday through the Wednesday after it.

day-range apr 23

will print YYYY-04-23, where YYYY is the current year.

day-range is insensitive to the case of arguments. For the kinds of date specifications understood by day-range, run ./t/run and read ./t/results-obtained.

Usage: day-format

day-range sunday .. +3d | day-format Friday, October 15th

day-format reads YYYY-MM-DD dates on stdin and writes them to stdout formatted according to its arguments.

Arguments are concatenated, with spaces as cement, into a formatting specification. Certain substrings in the specification are substituted with components of the date being processed, and the result is written to stdout on a line by itself.

The formatting specification could be seen as a readable version of a strftime string. In the grand tradition of programming languages, it is entirely English-centric.

Certain substrings of decimal digits are replaced with the following values:

• 1, 2, ... 9: the numeric day
• 10, 11, 12: the numeric month, two digits, with leading 0 if needed
• 13, 14, ... 31: the numeric day, two digits, with leading 0 if needed
• 2000 ... 9999: the year, four digits; this formatter is not Y10K-safe
• 10000 and above: the unix epoch

Longer substrings get preference.

Other substrings with special meaning, and what they are replaced with:

• 1st, 2nd ... 9th: the numeric day with ordinal English suffix
• 13th ... 31st: the numeric day with ordinal English suffix, four characters, with leading 0 if needed
• January ... December: English month name
• Jan ... Dec: three-character abbreviation of English month name
• Sunday ... Saturday: English day of week
• Sun ... Sat: three-character abbreviation of English day of week

Note:

• The format string is not tokenized
• Any ordinal suffix works with any qualifying numeral: 1th, 9rd, 22st are valid
• All-lowercase versions of month and day names also work and have the same meaning

Usage: lines

lines 9 2 6

copies lines numbered 2, 6, 11, 15, 18, ... from stdin to stdout. In general, lines m n1 n2 n3 prints lines numbered n1 mod m, n2 mod m, n3 mod m.

There is no attempt to limit the number of command line arguments. The advantage here is the simplicity of invocation.

Example:

day-range next friday .. dec 31 | lines 7 1 2

prints all Fridays and Saturdays from the coming week through the end of the year.