txt-agenda is a POSIX compliant script that searches text files to find and print lines containing [YYYY-MM-DD]-formatted dates. Lines are sorted by date, but each line is prefixed with the file name and line number where it was found. When called on one or more files, as in txt-agenda FILES, it returns lines from FILES that contain dates within one month of the current date. The date range can be inclusively extended with the -p (for past) and -f (for future) flags, so txt-agenda -p 1 -f 4 FILES will return all lines from FILES that contain dates that are no more that 1 month in the past and no more than 4 months in the future.

In commit 1ae5d0d and earlier, txt-agenda used a syntax similar to that of Howm mode, with -, +, and ! suffixes to designate different kinds of reminders. That functionality was removed since collecting dated tasks, for example, can easily be done by filtering lines returned by txt-agenda with grep, as in txt-agenda -p 4 -f 12 ~/your_notes/*.md | grep "TODO\|\[ \]", which will return all lines that contain dates no more than 4 months in the past, no more than 12 months in the future, and which contain either the string TODO or a Markdown checkbox.

txt-agenda was motivated by the desire for a simpler, faster, pipeline-composable, and editor-independent version of (a subset of) Org-mode's org-agenda.