fold(1)

NAME

fold — fold long lines for finite width output device

SYNOPSIS

fold [-b] [-s] [-w width] [file ...]

Obsolete form:

fold [-s] [- width] [file ...]

DESCRIPTION

The fold command is a filter that folds the contents of the specified files, breaking the lines to have a maximum of width column positions (or bytes, if the -b option is specified). The fold command breaks lines by inserting a newline character so that each output line is the maximum width possible that does not exceed the specified number of column positions (or bytes). A line cannot be broken in the middle of a character. If no files are specified or if a file name of - is specified, the standard input is used.

The fold command is often used to send text files to line printers that truncate, rather than fold, lines wider than the printer is able to print.

If the backspace, tab, or carriage-return characters are encountered in the input, and the -b option is not specified, they are treated specially as follows:

Backspace: The current count of line width is decremented by one, although the count never becomes negative. Thus, the character sequence character-backspace-character counts as using one column position, assuming both characters each occupy a single column position. fold does not insert a newline character immediately before or after any backspace character.
Tab: Each tab character encountered advances the column position pointer to the next tab stop. Tab stops are set 8 columns apart at column positions 1, 9, 17, 25, 33, etc.
Carriage-return: The current count of line width is set to zero. fold does not insert a newline character immediately before or after any carriage-return character.

Note that fold may affect any underlining that is present.

Options

The fold command recognizes the following options and command-line arguments:

-b: Count width in bytes rather than in column positions.
-s: Break the line on the last blank character found before the specified number of column positions (or bytes). If none are found, break the line at the specified line length.
-w width
-width: Specify the maximum line length, in column positions (or bytes if -b is specified). The default value is 80. width should be a multiple of 8 if tabs are present, or the tabs should be expanded using expand before processing by fold (see expand(1)). The -width option is obsolescent and may be removed in a future release.

EXTERNAL INFLUENCES

Environment Variables

LC_CTYPE determines the interpretation of text as single- and/or multi-byte characters.

LC_MESSAGES determines the language in which messages are displayed.

If LC_CTYPE or LC_MESSAGES is not specified in the environment or is set to the empty string, the value of LANG is used as a default for each unspecified or empty variable. If LANG is not specified or is set to the empty string, a default of "C" (see lang(5)) is used instead of LANG.

If any internationalization variable contains an invalid setting, fold behaves as if all internationalization variables are set to "C". See environ(5).

International Code Set Support

Single- and multi-byte character code sets are supported.

STANDARDS CONFORMANCE

fold: XPG4, POSIX.2