.\"	$OpenBSD: fold.1,v 1.18 2016/05/23 10:31:42 schwarze Exp $
.\"	$NetBSD: fold.1,v 1.5 1995/09/01 01:42:42 jtc Exp $
.\"
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.\"	@(#)fold.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: May 23 2016 $
.Dt FOLD 1
.Os
.Sh NAME
.Nm fold
.Nd fold long lines for finite width output device
.Sh SYNOPSIS
.Nm fold
.Op Fl bs
.Op Fl w Ar width
.Op Ar
.Sh DESCRIPTION
.Nm
is a filter which folds the contents of the specified files,
or the standard input if no files are specified,
breaking the lines to have a maximum of 80 display columns.
.Pp
The options are as follows:
.Bl -tag -width 8n
.It Fl b
Count
.Ar width
in bytes rather than column positions.
.It Fl s
If an output line would be broken after a non-blank character but
contains at least one blank character, break the line earlier,
after the last blank character.
This is useful to avoid line breaks in the middle of words, if
possible.
.It Fl w Ar width
Specifies a line width to use instead of the default of 80.
.El
.Pp
Unless
.Fl b
is specified, a backspace character decrements the column position
by one, a carriage return resets the column position to zero, and
a tab advances the column position to the next multiple of eight.
.Sh ENVIRONMENT
.Bl -tag -width 8n
.It Ev LC_CTYPE
The character set
.Xr locale 1 .
It is used to decide which byte sequences form characters and what
their display width is.
If it is unset or set to
.Qq C ,
.Qq POSIX ,
or an unsupported value, each byte except backspace, tab, newline,
and carriage return is assumed to represent a character of display
width 1.
.El
.Sh EXIT STATUS
.Ex -std fold
.Sh SEE ALSO
.Xr expand 1 ,
.Xr fmt 1
.Sh STANDARDS
The
.Nm
utility is compliant with the
.St -p1003.1-2008
specification.
.Sh HISTORY
The
.Nm
utility first appeared in
.Bx 1 .
It was rewritten for
.Bx 4.3 Reno
to improve speed and modernize style.
The
.Fl b
and
.Fl s
options were added to
.Nx 1.0
for
.St -p1003.2
compliance.
.Sh AUTHORS
.An -nosplit
.An Bill Joy
wrote the original version of
.Nm
on June 28, 1977.
.An Kevin Ruddy
rewrote the command in 1990, and
.An J. T. Conklin
added the missing options in 1993.
.Sh BUGS
Traditional
.Xr roff 7
output semantics, implemented both by GNU nroff and by
.Xr mandoc 1 ,
only uses a single backspace for backing up the previous character,
even for double-width characters.
The
.Nm
backspace semantics required by POSIX mishandles such backspace-encoded
sequences, breaking lines early.
The
.Xr fmt 1
utility provides similar functionality and does not suffer from that
problem, but isn't standardized by POSIX.