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.TH FOLD 1 "Feb 1, 1995"
.SH NAME
fold \- filter for folding lines
.SH SYNOPSIS
.LP
.nf
\fBfold\fR [\fB-bs\fR] [\fB-w\fR \fIwidth\fR | \fB-width\fR] [\fIfile\fR]...
.fi

.SH DESCRIPTION
.sp
.LP
The \fBfold\fR utility is a filter that will fold lines from its input files,
breaking the lines to have a maximum of \fIwidth\fR column positions (or bytes,
if the \fB-b\fR option is specified). Lines will be broken by the insertion of
a NEWLINE character such that each output line (referred to later in this
section as a segment) is the maximum width possible that does not exceed the
specified number of column positions (or bytes). A line will not be broken in
the middle of a character. The behavior is undefined if \fIwidth\fR is less
than the number of columns any single character in the input would occupy.
.sp
.LP
If the CARRIAGE-RETURN, BACKSPACE, or TAB characters are encountered in the
input, and the \fB-b\fR option is not specified, they will be treated
specially:
.sp
.ne 2
.na
\fBBACKSPACE \fR
.ad
.RS 20n
The current count of line width will be decremented by one, although the count
never will become negative. \fBfold\fR will not insert a NEWLINE character
immediately before or after any BACKSPACE character.
.RE

.sp
.ne 2
.na
\fBCARRIAGE-RETURN \fR
.ad
.RS 20n
The current count of line width will be set to \fB0\fR. \fBfold\fR will not
insert a NEWLINE character immediately before or after any CARRIAGE-RETURN
character.
.RE

.sp
.ne 2
.na
\fBTAB \fR
.ad
.RS 20n
Each TAB character encountered will advance the column position pointer to the
next tab stop. Tab stops will be at each column position \fIn\fR such that
\fIn\fR modulo 8 equals 1.
.RE

.SH OPTIONS
.sp
.LP
The following options are supported:
.sp
.ne 2
.na
\fB\fB-b\fR \fR
.ad
.RS 20n
Counts \fIwidth\fR in bytes rather than column positions.
.RE

.sp
.ne 2
.na
\fB\fB-s\fR \fR
.ad
.RS 20n
If a segment of a line contains a blank character within the first \fIwidth\fR
column positions (or bytes), breaks the line after the last such blank
character meeting the width constraints. If there is no blank character meeting
the requirements, the \fB-s\fR option will have no effect for that output
segment of the input line.
.RE

.sp
.ne 2
.na
\fB\fB-w\fR \fIwidth\fR\fB|\fR\fB-\fR\fIwidth\fR \fR
.ad
.RS 20n
Specifies the maximum line length, in column positions (or bytes if \fB-b\fR is
specified). If \fIwidth\fR is not a positive decimal number, an error is
returned. The default value is 80.
.RE

.SH OPERANDS
.sp
.LP
The following operand is supported:
.sp
.ne 2
.na
\fB\fB\fIfile\fR\fR \fR
.ad
.RS 9n
A path name of a text file to be folded. If no \fIfile\fR operands are
specified, the standard input will be used.
.RE

.SH EXAMPLES
.LP
\fBExample 1 \fRSubmitting a file of possibly long lines to the line printer
.sp
.LP
An example invocation that submits a file of possibly long lines to the line
printer (under the assumption that the user knows the line width of the printer
to be assigned by \fBlp\fR(1)):

.sp
.in +2
.nf
example% \fBfold -w 132 bigfile | lp\fR
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBfold\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR \fR
.ad
.RS 7n
All input files were processed successfully.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR \fR
.ad
.RS 7n
An error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	enabled
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
\fBcut\fR(1), \fBpr\fR(1), \fBattributes\fR(5), \fBenviron\fR(5),
\fBstandards\fR(5)
.SH NOTES
.sp
.LP
\fBfold\fR and \fBcut\fR(1) can be used to create text files out of files with
arbitrary line lengths. \fBfold\fR should be used when the contents of long
lines need to be kept contiguous. \fBcut\fR should be used when the number of
lines (or records) needs to remain constant.
.sp
.LP
\fBfold\fR is frequently used to send text files to line printers that
truncate, rather than fold, lines wider than the printer is able to print
(usually 80 or 132 column positions).
.sp
.LP
\fBfold\fR may not work correctly if underlining is present.