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

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

       fold — filter for folding lines

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

       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 unde‐
       fined  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  encoun‐
       tered  in  the input, and the −b option is not specified, they shall be
       treated specially:

		 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>, unless the following character has a
		 width greater than 1 and would cause the line width to exceed

		 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 col‐
		 umn position n such that n modulo 8 equals 1.

       The  fold  utility  shall  conform  to  the  Base Definitions volume of
       POSIX.1‐2008, 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.

       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.

       The standard input shall be used if no file operands are specified, and
       shall  be  used	if a file operand is '−' and the implementation treats
       the '−' as meaning standard input.  Otherwise, the standard input shall
       not be used.  See the INPUT FILES section.

       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.

       The following environment variables shall affect the execution of fold:

       LANG	 Provide  a  default  value for the internationalization vari‐
		 ables that are unset or null. (See the Base Definitions  vol‐
		 ume  of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
		 ables 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.

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

       NLSPATH	 Determine the location of message catalogs for the processing


       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> characters.

       The standard error shall be used only for diagnostic messages.



       The following exit values shall be returned:

	0    All input files were processed successfully.

       >0    An error occurred.


       The following sections are informative.

       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

       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).

       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

       Although terminal input in canonical processing mode requires the erase
       character (frequently set to <backspace>) to erase the previous charac‐
       ter (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> character backs up one column position
       and outputs enough <backspace> characters 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

       Historical  versions of the fold utility assumed 1 byte was one charac‐
       ter 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 single character found
       in the input followed by a <newline>.)

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



       The Base Definitions volume of  POSIX.1‐2008,  Chapter  8,  Environment
       Variables, Section 12.2, Utility Syntax Guidelines

       Portions	 of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating	System	Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
       cal  and	 Electronics  Engineers,  Inc  and  The	 Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum	 1  applied.)  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 .

       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,	 see  https://www.ker‐ .

IEEE/The Open Group		     2013			      FOLD(1P)

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