FOLD(1P)						     POSIX Programmer's Manual							  FOLD(1P)

PROLOG

       This  manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (consult the correspond-
       ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

       fold - filter for folding lines

SYNOPSIS

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

DESCRIPTION

       The fold utility is a filter that shall 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 shall be broken by the insertion of a <newline> 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  shall  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>s, <backspace>s, or <tab>s are encountered in the input, and the -b option is not specified, they shall be  treated
       specially:

       <backspace>
	      The  current count of line width shall be decremented by one, although the count never shall become negative. The fold utility shall
	      not insert a <newline> immediately before or after any <backspace>.

       <carriage-return>

	      The current count of line width shall be set to zero. The fold utility shall not insert a <newline> immediately before or after  any
	      <carriage-return>.

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

OPTIONS

       The fold utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -b     Count width in bytes rather than column positions.

       -s     If a segment of a line contains a <blank> within the first width column positions (or bytes), break the line  after  the	last  such
	      <blank>  meeting the width constraints. If there is no <blank> meeting the requirements, the -s option shall have no effect for that
	      output segment of the input line.

       -w  width
	      Specify the maximum line length, in column positions (or bytes if -b is specified). The results are unspecified if width	is  not  a
	      positive decimal number. The default value shall be 80.

OPERANDS

       The following operand shall be supported:

       file   A pathname of a text file to be folded. If no file operands are specified, the standard input shall be used.

STDIN

       The standard input shall be used only if no file operands are specified. See the INPUT FILES section.

INPUT FILES

       If  the -b option is specified, the input files shall be text files except that the lines are not limited to {LINE_MAX} bytes in length. If
       the -b option is not specified, the input files shall be text files.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of fold:

       LANG   Provide a default value for the internationalization variables that  are	unset  or  null.  (See	the  Base  Definitions	volume	of
	      IEEE Std 1003.1-2001,  Section  8.2,  Internationalization  Variables  for  the precedence of internationalization variables used to
	      determine the values of locale categories.)

       LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.

       LC_CTYPE
	      Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to
	      multi-byte characters in arguments and input files), and for the determination of the width in column positions each character would
	      occupy on a constant-width font output device.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.

       NLSPATH
	      Determine the location of message catalogs for the processing of LC_MESSAGES .

ASYNCHRONOUS EVENTS

       Default.

STDOUT

       The standard output shall be a file containing a sequence of characters whose order shall be preserved from the input files, possibly  with
       inserted <newline>s.

STDERR

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES

       None.

EXTENDED DESCRIPTION

       None.

EXIT STATUS

       The following exit values shall be returned:

	0     All input files were processed successfully.

       >0     An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

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

       The fold utility is frequently used to send text files to printers that truncate, rather than fold, lines wider than the printer is able to
       print (usually 80 or 132 column positions).

EXAMPLES

       An example invocation that submits a file of possibly long lines to the printer (under the assumption that the user knows the line width of
       the printer to be assigned by lp):

	      fold -w 132 bigfile | lp

RATIONALE

       Although  terminal  input  in  canonical processing mode requires the erase character (frequently set to <backspace>) to erase the previous
       character (not byte or column position), terminal output is not buffered and is extremely difficult, if not impossible, to parse correctly;
       the  interpretation depends entirely on the physical device that actually displays/prints/stores the output. In all known internationalized
       implementations, the utilities producing output for mixed column-width output assume that a <backspace> backs up one  column  position  and
       outputs	enough	<backspace>s  to  return  to  the start of the character when <backspace> is used to provide local line motions to support
       underlining and emboldening operations. Since fold without the -b option is dealing with these  same  constraints,  <backspace>	is  always
       treated as backing up one column position rather than backing up one character.

       Historical  versions  of  the  fold  utility assumed 1 byte was one character and occupied one column position when written out. This is no
       longer always true. Since the most common usage of fold is believed to be folding long lines for output to limited-length  output  devices,
       this  capability  was  preserved  as  the default case. The -b option was added so that applications could fold files with arbitrary length
       lines into text files that could then be processed by the standard utilities. Note that although the width for the -b option is in bytes, a
       line is never split in the middle of a character.  (It is unspecified what happens if a width is specified that is too small to hold a sin-
       gle character found in the input followed by a <newline>.)

       The tab stops are hardcoded to be every eighth column to meet historical practice.  No  new  method  of	specifying  other  tab	stops  was
       invented.

FUTURE DIRECTIONS

       None.

SEE ALSO

       cut

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical  and	Electronics  Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
       and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can  be  obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								  FOLD(1P)