intcmp(1): new tool; npc(1): new tool; scrut(1): new tool; str(1): new tool; strcmp(1): new tool; tests: added POSIX compatibility test and C compiler compatibility test; Makefile: converted to GNUmakefile; README: added README; docs: added docs

docs/npc.1

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+.\" Copyright (c) 2023 DTB <trinity@trinity.moe>
+.\" Copyright (c) 2023 Emma Tebibyte <emma@tebibyte.media>
+.\"
+.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
+.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
+
+.TH npc 1
+
+.SH NAME
+
+npc \(en show non-printing characters
+
+.SH SYNOPSIS
+
+npc
+.RB ( -eht )
+
+.SH DESCRIPTION
+
+Npc reads from standard input and writes to standard output, replacing non-
+printing characters with printable equivalents. Control characters print as a
+carat ('^') followed by the character '@' through '_' corresponding to the
+character replaced (e.g. control-X becomes "^X"). The delete character (0x7F)
+becomes "^?". Characters with the high bit set (>127) are printed as "M-"
+followed by the graphical representation for the same character without the
+high bit set.
+.PP
+The
+.B -e
+option prints a currency sign ('$') before each line ending.
+.PP
+The
+.B -t
+option prints tab characters as "^I" rather than a literal horizontal tab.
+
+.SH DIAGNOSTICS
+
+Npc prints a debug message and exits with the appropriate sysexits(3) error
+code in the event of an error, otherwise it exits successfully.
+
+.SH BUGS
+
+Npc operates in single-byte chunks regardless of intended encoding.
+
+.SH RATIONALE
+
+POSIX currently lacks a way to display non-printing characters in the terminal
+using a standard tool. A popular extension to cat(1p), the -v option, is the
+bandage solution GNU and other software suites use.
+
+This functionality should be a separate tool because its usefulness extends
+beyond that of cat(1p).
+
+.SH AUTHOR
+
+Written by DTB <trinity@trinity.moe>.
+
+.SH COPYRIGHT
+
+Copyright © 2023 DTB. License AGPLv3+: GNU AGPL version 3 or later
+<https://gnu.org/licenses/agpl.html>.
+
+.SH SEE ALSO
+
+cat(1), cat-v(1)
+
+.I UNIX Style, or cat -v Considered Harmful
+by Rob Pike