$OpenBSD: README,v 1.5 2018/06/15 08:46:24 martijn Exp $$NetBSD: README,v 1.9 1995/03/21 09:04:33 cgd Exp $ed is an 8-bit-clean, POSIX-compliant line editor.  It should work withany regular expression package that conforms to the POSIX interfacestandard, such as GNU regex(3).If reliable signals are supported (e.g., POSIX sigaction(2)), it shouldcompile with little trouble.  Otherwise, the macros SPL1() and SPL0()should be redefined to disable interrupts.The file 'POSIX' describes extensions to and deviations from the POSIXstandard.The ./test directory contains regression tests for ed. The READMEfile in that directory explains how to run these.For a description of the ed algorithm, see Kernighan and Plauger's book"Software Tools in Pascal," Addison-Wesley, 1981.