.\" Copyright (c) 2023–2024 DTB <trinity@trinity.moe>
.\" Copyright (c) 2023–2024 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 ( -et )

.SH DESCRIPTION

Print normally non-printing characters.

The program 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.

.SH USAGE

.B -e
.RS
Prints a currency sign (“$”) before each line ending.
.RE

.B -t
.RS
Prints tab characters as “^I” rather than a literal horizontal tab.
.RE

.SH DIAGNOSTICS

In the event of an error, a debug message will be printed and the program will
exit with the appropriate sysexits.h(3) error code.

.SH BUGS

The program 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
.B -v
option, is the bandage solution GNU and other software suites use.

This functionality is 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(1p), cat-v(1)

.I UNIX Style, or cat -v Considered Harmful
by Rob Pike