Ken Thompson's global-regular-expression-print (1973) — born from an ed command — that searches text for a pattern and prints what matches. Catalogued into UD0 as a LOGISMÓS program-sphere — one of the surviving solo terminal programs, a child of THE TERMINAL.
The Four Natures
each facet emerges by one of four natures
The Program
born · what it does · the line
Thompson pulled ed's g/re/p command out into its own program overnight, the story goes, to help a colleague search text.
Read a stream of text, print every line that matches a regular expression — the single most-used filter on the command line.
From ed's global command; spawned egrep, fgrep, and modern speed-demons like ripgrep; 'to grep' is now a verb in English.
The Facets
grep and its facets as ACI .agents — each a birth certificate & a nature (3)
