FOLD(1) User Commands FOLD(1)

NAME

fold - filter for folding lines

SYNOPSIS

fold [-bs] [-w width | -width] [file]...

DESCRIPTION

The fold utility is a filter that will fold lines from its input files,
breaking the lines to have a maximum of width column positions (or bytes,
if the -b 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 width
is less than the number of columns any single character in the input
would occupy.


If the CARRIAGE-RETURN, BACKSPACE, or TAB characters are encountered in
the input, and the -b option is not specified, they will be treated
specially:

BACKSPACE
The current count of line width will be decremented
by one, although the count never will become
negative. fold will not insert a NEWLINE character
immediately before or after any BACKSPACE character.


CARRIAGE-RETURN
The current count of line width will be set to 0.
fold will not insert a NEWLINE character immediately
before or after any CARRIAGE-RETURN character.


TAB
Each TAB character encountered will advance the
column position pointer to the next tab stop. Tab
stops will be at each column position n such that n
modulo 8 equals 1.

OPTIONS

The following options are supported:

-b
Counts width in bytes rather than column positions.


-s
If a segment of a line contains a blank character
within the first width 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 -s option
will have no effect for that output segment of the
input line.


-w width|-width
Specifies the maximum line length, in column
positions (or bytes if -b is specified). If width is
not a positive decimal number, an error is returned.
The default value is 80.

OPERANDS

The following operand is supported:

file
A path name of a text file to be folded. If no file operands are
specified, the standard input will be used.

EXAMPLES

Example 1: Submitting a file of possibly long lines to the line printer

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 lp(1)):


example% fold -w 132 bigfile | lp

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment variables
that affect the execution of fold: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES,
and NLSPATH.

EXIT STATUS

The following exit values are returned:

0
All input files were processed successfully.


>0
An error occurred.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|CSI | enabled |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+

SEE ALSO

cut(1), pr(1), attributes(7), environ(7), standards(7)

NOTES

fold and cut(1) can be used to create text files out of files with
arbitrary line lengths. fold should be used when the contents of long
lines need to be kept contiguous. cut should be used when the number of
lines (or records) needs to remain constant.


fold 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).


fold may not work correctly if underlining is present.

February 1, 1995 FOLD(1)