more(1p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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.

NAME         top

       more — display files on a page-by-page basis

SYNOPSIS         top

       more [-ceisu] [-n number] [-p command] [-t tagstring] [file...]

DESCRIPTION         top

       The more utility shall read files and either write them to the
       terminal on a page-by-page basis or filter them to standard
       output. If standard output is not a terminal device, all input
       files shall be copied to standard output in their entirety,
       without modification, except as specified for the -s option. If
       standard output is a terminal device, the files shall be written
       a number of lines (one screenful) at a time under the control of
       user commands. See the EXTENDED DESCRIPTION section.

       Certain block-mode terminals do not have all the capabilities
       necessary to support the complete more definition; they are
       incapable of accepting commands that are not terminated with a
       <newline>.  Implementations that support such terminals shall
       provide an operating mode to more in which all commands can be
       terminated with a <newline> on those terminals. This mode:

        *  Shall be documented in the system documentation

        *  Shall, at invocation, inform the user of the terminal
           deficiency that requires the <newline> usage and provide
           instructions on how this warning can be suppressed in future
           invocations

        *  Shall not be required for implementations supporting only
           fully capable terminals

        *  Shall not affect commands already requiring <newline>
           characters

        *  Shall not affect users on the capable terminals from using
           more as described in this volume of POSIX.1‐2017

OPTIONS         top

       The more utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines, except
       that '+' may be recognized as an option delimiter as well as '-'.

       The following options shall be supported:

       -c        If a screen is to be written that has no lines in
                 common with the current screen, or more is writing its
                 first screen, more shall not scroll the screen, but
                 instead shall redraw each line of the screen in turn,
                 from the top of the screen to the bottom. In addition,
                 if more is writing its first screen, the screen shall
                 be cleared. This option may be silently ignored on
                 devices with insufficient terminal capabilities.

       -e        Exit immediately after writing the last line of the
                 last file in the argument list; see the EXTENDED
                 DESCRIPTION section.

       -i        Perform pattern matching in searches without regard to
                 case; see the Base Definitions volume of POSIX.1‐2017,
                 Section 9.2, Regular Expression General Requirements.

       -n number Specify the number of lines per screenful. The number
                 argument is a positive decimal integer. The -n option
                 shall override any values obtained from any other
                 source.

       -p command
                 Each time a screen from a new file is displayed or
                 redisplayed (including as a result of more commands;
                 for example, :p), execute the more command(s) in the
                 command arguments in the order specified, as if entered
                 by the user after the first screen has been displayed.
                 No intermediate results shall be displayed (that is, if
                 the command is a movement to a screen different from
                 the normal first screen, only the screen resulting from
                 the command shall be displayed.) If any of the commands
                 fail for any reason, an informational message to this
                 effect shall be written, and no further commands
                 specified using the -p option shall be executed for
                 this file.

       -s        Behave as if consecutive empty lines were a single
                 empty line.

       -t tagstring
                 Write the screenful of the file containing the tag
                 named by the tagstring argument. See the ctags(1p)
                 utility. The tags feature represented by -t tagstring
                 and the :t command is optional. It shall be provided on
                 any system that also provides a conforming
                 implementation of ctags; otherwise, the use of -t
                 produces undefined results.

                 The filename resulting from the -t option shall be
                 logically added as a prefix to the list of command line
                 files, as if specified by the user. If the tag named by
                 the tagstring argument is not found, it shall be an
                 error, and more shall take no further action.

                 If the tag specifies a line number, the first line of
                 the display shall contain the beginning of that line.
                 If the tag specifies a pattern, the first line of the
                 display shall contain the beginning of the matching
                 text from the first line of the file that contains that
                 pattern. If the line does not exist in the file or
                 matching text is not found, an informational message to
                 this effect shall be displayed, and more shall display
                 the default screen as if -t had not been specified.

                 If both the -t tagstring and -p command options are
                 given, the -t tagstring shall be processed first; that
                 is, the file and starting line for the display shall be
                 as specified by -t, and then the -p more command shall
                 be executed. If the line (matching text) specified by
                 the -t command does not exist (is not found), no -p
                 more command shall be executed for this file at any
                 time.

       -u        Treat a <backspace> as a printable control character,
                 displayed as an implementation-defined character
                 sequence (see the EXTENDED DESCRIPTION section),
                 suppressing backspacing and the special handling that
                 produces underlined or standout mode text on some
                 terminal types.  Also, do not ignore a <carriage-
                 return> at the end of a line.

OPERANDS         top

       The following operand shall be supported:

       file      A pathname of an input file. If no file operands are
                 specified, the standard input shall be used. If a file
                 is '-', the standard input shall be read at that point
                 in the sequence.

STDIN         top

       The standard input shall be used only if no file operands are
       specified, or if a file operand is '-'.

INPUT FILES         top

       The input files being examined shall be text files. If standard
       output is a terminal, standard error shall be used to read
       commands from the user. If standard output is a terminal,
       standard error is not readable, and command input is needed, more
       may attempt to obtain user commands from the controlling terminal
       (for example, /dev/tty); otherwise, more shall terminate with an
       error indicating that it was unable to read user commands. If
       standard output is not a terminal, no error shall result if
       standard error cannot be opened for reading.

ENVIRONMENT VARIABLES         top

       The following environment variables shall affect the execution of
       more:

       COLUMNS   Override the system-selected horizontal display line
                 size. See the Base Definitions volume of POSIX.1‐2017,
                 Chapter 8, Environment Variables for valid values and
                 results when it is unset or null.

       EDITOR    Used by the v command to select an editor. See the
                 EXTENDED DESCRIPTION section.

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, 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_COLLATE
                 Determine the locale for the behavior of ranges,
                 equivalence classes, and multi-character collating
                 elements within regular expressions.

       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 the
                 behavior of character classes within regular
                 expressions.

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

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

       LINES     Override the system-selected vertical screen size, used
                 as the number of lines in a screenful. See the Base
                 Definitions volume of POSIX.1‐2017, Chapter 8,
                 Environment Variables for valid values and results when
                 it is unset or null. The -n option shall take
                 precedence over the LINES variable for determining the
                 number of lines in a screenful.

       MORE      Determine a string containing options described in the
                 OPTIONS section preceded with <hyphen-minus> characters
                 and <blank>-separated as on the command line. Any
                 command line options shall be processed after those in
                 the MORE variable, as if the command line were:

                     more $MORE options operands

                 The MORE variable shall take precedence over the TERM
                 and LINES variables for determining the number of lines
                 in a screenful.

       TERM      Determine the name of the terminal type. If this
                 variable is unset or null, an unspecified default
                 terminal type is used.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       The standard output shall be used to write the contents of the
       input files.

STDERR         top

       The standard error shall be used for diagnostic messages and user
       commands (see the INPUT FILES section), and, if standard output
       is a terminal device, to write a prompting string. The prompting
       string shall appear on the screen line below the last line of the
       file displayed in the current screenful. The prompt shall contain
       the name of the file currently being examined and shall contain
       an end-of-file indication and the name of the next file, if any,
       when prompting at the end-of-file. If an error or informational
       message is displayed, it is unspecified whether it is contained
       in the prompt. If it is not contained in the prompt, it shall be
       displayed and then the user shall be prompted for a continuation
       character, at which point another message or the user prompt may
       be displayed. The prompt is otherwise unspecified. It is
       unspecified whether informational messages are written for other
       user commands.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       The following section describes the behavior of more when the
       standard output is a terminal device. If the standard output is
       not a terminal device, no options other than -s shall have any
       effect, and all input files shall be copied to standard output
       otherwise unmodified, at which time more shall exit without
       further action.

       The number of lines available per screen shall be determined by
       the -n option, if present, or by examining values in the
       environment (see the ENVIRONMENT VARIABLES section). If neither
       method yields a number, an unspecified number of lines shall be
       used.

       The maximum number of lines written shall be one less than this
       number, because the screen line after the last line written shall
       be used to write a user prompt and user input. If the number of
       lines in the screen is less than two, the results are undefined.
       It is unspecified whether user input is permitted to be longer
       than the remainder of the single line where the prompt has been
       written.

       The number of columns available per line shall be determined by
       examining values in the environment (see the ENVIRONMENT
       VARIABLES section), with a default value as described in the Base
       Definitions volume of POSIX.1‐2017, Chapter 8, Environment
       Variables.

       Lines that are longer than the display shall be folded; the
       length at which folding occurs is unspecified, but should be
       appropriate for the output device. Folding may occur between
       glyphs of single characters that take up multiple display
       columns.

       When standard output is a terminal and -u is not specified, more
       shall treat <backspace> and <carriage-return> characters
       specially:

        *  A character, followed first by a sequence of n <backspace>
           characters (where n is the same as the number of column
           positions that the character occupies), then by n
           <underscore> characters ('_'), shall cause that character to
           be written as underlined text, if the terminal type supports
           that. The n <underscore> characters, followed first by n
           <backspace> characters, then any character with n column
           positions, shall also cause that character to be written as
           underlined text, if the terminal type supports that.

        *  A sequence of n <backspace> characters (where n is the same
           as the number of column positions that the previous character
           occupies) that appears between two identical printable
           characters shall cause the first of those two characters to
           be written as emboldened text (that is, visually brighter,
           standout mode, or inverse-video mode), if the terminal type
           supports that, and the second to be discarded. Immediately
           subsequent occurrences of <backspace>/character pairs for
           that same character shall also be discarded. (For example,
           the sequence "a\ba\ba\ba" is interpreted as a single
           emboldened 'a'.)

        *  The more utility shall logically discard all other
           <backspace> characters from the line as well as the character
           which precedes them, if any.

        *  A <carriage-return> at the end of a line shall be ignored,
           rather than being written as a non-printable character, as
           described in the next paragraph.

       It is implementation-defined how other non-printable characters
       are written. Implementations should use the same format that they
       use for the ex print command; see the OPTIONS section within the
       ed utility. It is unspecified whether a multi-column character
       shall be separated if it crosses a display line boundary; it
       shall not be discarded. The behavior is unspecified if the number
       of columns on the display is less than the number of columns any
       single character in the line being displayed would occupy.

       When each new file is displayed (or redisplayed), more shall
       write the first screen of the file. Once the initial screen has
       been written, more shall prompt for a user command. If the
       execution of the user command results in a screen that has lines
       in common with the current screen, and the device has sufficient
       terminal capabilities, more shall scroll the screen; otherwise,
       it is unspecified whether the screen is scrolled or redrawn.

       For all files but the last (including standard input if no file
       was specified, and for the last file as well, if the -e option
       was not specified), when more has written the last line in the
       file, more shall prompt for a user command. This prompt shall
       contain the name of the next file as well as an indication that
       more has reached end-of-file. If the user command is f,
       <control>‐F, <space>, j, <newline>, d, <control>‐D, or s, more
       shall display the next file. Otherwise, if displaying the last
       file, more shall exit. Otherwise, more shall execute the user
       command specified.

       Several of the commands described in this section display a
       previous screen from the input stream. In the case that text is
       being taken from a non-rewindable stream, such as a pipe, it is
       implementation-defined how much backwards motion is supported. If
       a command cannot be executed because of a limitation on backwards
       motion, an error message to this effect shall be displayed, the
       current screen shall not change, and the user shall be prompted
       for another command.

       If a command cannot be performed because there are insufficient
       lines to display, more shall alert the terminal. If a command
       cannot be performed because there are insufficient lines to
       display or a / command fails: if the input is the standard input,
       the last screen in the file may be displayed; otherwise, the
       current file and screen shall not change, and the user shall be
       prompted for another command.

       The interactive commands in the following sections shall be
       supported.  Some commands can be preceded by a decimal integer,
       called count in the following descriptions. If not specified with
       the command, count shall default to 1. In the following
       descriptions, pattern is a basic regular expression, as described
       in the Base Definitions volume of POSIX.1‐2017, Section 9.3,
       Basic Regular Expressions.  The term ``examine'' is historical
       usage meaning ``open the file for viewing''; for example, more
       foo would be expressed as examining file foo.

       In the following descriptions, unless otherwise specified, line
       is a line in the more display, not a line from the file being
       examined.

       In the following descriptions, the current position refers to two
       things:

        1. The position of the current line on the screen

        2. The line number (in the file) of the current line on the
           screen

       Usually, the line on the screen corresponding to the current
       position is the third line on the screen. If this is not possible
       (there are fewer than three lines to display or this is the first
       page of the file, or it is the last page of the file), then the
       current position is either the first or last line on the screen
       as described later.

   Help
       Synopsis:

                     h

       Write a summary of these commands and other implementation-
       defined commands. The behavior shall be as if the more utility
       were executed with the -e option on a file that contained the
       summary information. The user shall be prompted as described
       earlier in this section when end-of-file is reached. If the user
       command is one of those specified to continue to the next file,
       more shall return to the file and screen state from which the h
       command was executed.

   Scroll Forward One Screenful
       Synopsis:

                     [count]f
                     [count]<control>-F

       Scroll forward count lines, with a default of one screenful. If
       count is more than the screen size, only the final screenful
       shall be written.

   Scroll Backward One Screenful
       Synopsis:

                     [count]b
                     [count]<control>-B

       Scroll backward count lines, with a default of one screenful (see
       the -n option). If count is more than the screen size, only the
       final screenful shall be written.

   Scroll Forward One Line
       Synopsis:

                     [count]<space>
                     [count]j
                     [count]<newline>

       Scroll forward count lines. The default count for the <space>
       shall be one screenful; for j and <newline>, one line. The entire
       count lines shall be written, even if count is more than the
       screen size.

   Scroll Backward One Line
       Synopsis:

                     [count]k

       Scroll backward count lines. The entire count lines shall be
       written, even if count is more than the screen size.

   Scroll Forward One Half Screenful
       Synopsis:

                     [count]d
                     [count]<control>-D

       Scroll forward count lines, with a default of one half of the
       screen size. If count is specified, it shall become the new
       default for subsequent d, <control>‐D, and u commands.

   Skip Forward One Line
       Synopsis:

                     [count]s

       Display the screenful beginning with the line count lines after
       the last line on the current screen. If count would cause the
       current position to be such that less than one screenful would be
       written, the last screenful in the file shall be written.

   Scroll Backward One Half Screenful
       Synopsis:

                     [count]u
                     [count]<control>-U

       Scroll backward count lines, with a default of one half of the
       screen size. If count is specified, it shall become the new
       default for subsequent d, <control>-D, u, and <control>-U
       commands. The entire count lines shall be written, even if count
       is more than the screen size.

   Go to Beginning of File
       Synopsis:

                     [count]g

       Display the screenful beginning with line count.

   Go to End-of-File
       Synopsis:

                     [count]G

       If count is specified, display the screenful beginning with the
       line count.  Otherwise, display the last screenful of the file.

   Refresh the Screen
       Synopsis:

                     r
                     <control>-L

       Refresh the screen.

   Discard and Refresh
       Synopsis:

                     R

       Refresh the screen, discarding any buffered input. If the current
       file is non-seekable, buffered input shall not be discarded and
       the R command shall be equivalent to the r command.

   Mark Position
       Synopsis:

                     mletter

       Mark the current position with the letter named by letter, where
       letter represents the name of one of the lowercase letters of the
       portable character set. When a new file is examined, all marks
       may be lost.

   Return to Mark
       Synopsis:

                     'letter

       Return to the position that was previously marked with the letter
       named by letter, making that line the current position.

   Return to Previous Position
       Synopsis:

                     ''

       Return to the position from which the last large movement command
       was executed (where a ``large movement'' is defined as any
       movement of more than a screenful of lines). If no such movements
       have been made, return to the beginning of the file.

   Search Forward for Pattern
       Synopsis:

                     [count]/[!]pattern<newline>

       Display the screenful beginning with the countth line containing
       the pattern. The search shall start after the first line
       currently displayed. The null regular expression ('/' followed by
       a <newline>) shall repeat the search using the previous regular
       expression, with a default count.  If the character '!'  is
       included, the matching lines shall be those that do not contain
       the pattern.  If no match is found for the pattern, a message to
       that effect shall be displayed.

   Search Backward for Pattern
       Synopsis:

                     [count]?[!]pattern<newline>

       Display the screenful beginning with the countth previous line
       containing the pattern. The search shall start on the last line
       before the first line currently displayed. The null regular
       expression ('?'  followed by a <newline>) shall repeat the search
       using the previous regular expression, with a default count.  If
       the character '!'  is included, matching lines shall be those
       that do not contain the pattern.  If no match is found for the
       pattern, a message to that effect shall be displayed.

   Repeat Search
       Synopsis:

                     [count]n

       Repeat the previous search for countth line containing the last
       pattern (or not containing the last pattern, if the previous
       search was "/!" or "?!").

   Repeat Search in Reverse
       Synopsis:

                     [count]N

       Repeat the search in the opposite direction of the previous
       search for the countth line containing the last pattern (or not
       containing the last pattern, if the previous search was "/!" or
       "?!").

   Examine New File
       Synopsis:

                     :e [filename]<newline>

       Examine a new file. If the filename argument is not specified,
       the current file (see the :n and :p commands below) shall be re-
       examined. The filename shall be subjected to the process of shell
       word expansions (see Section 2.6, Word Expansions); if more than
       a single pathname results, the effects are unspecified.  If
       filename is a <number-sign> ('#'), the previously examined file
       shall be re-examined. If filename is not accessible for any
       reason (including that it is a non-seekable file), an error
       message to this effect shall be displayed and the current file
       and screen shall not change.

   Examine Next File
       Synopsis:

                     [count]:n

       Examine the next file. If a number count is specified, the
       countth next file shall be examined. If filename refers to a non-
       seekable file, the results are unspecified.

   Examine Previous File
       Synopsis:

                     [count]:p

       Examine the previous file. If a number count is specified, the
       countth previous file shall be examined. If filename refers to a
       non-seekable file, the results are unspecified.

   Go to Tag
       Synopsis:

                     :t tagstring<newline>

       If the file containing the tag named by the tagstring argument is
       not the current file, examine the file, as if the :e command was
       executed with that file as the argument. Otherwise, or in
       addition, display the screenful beginning with the tag, as
       described for the -t option (see the OPTIONS section). If the
       ctags utility is not supported by the system, the use of :t
       produces undefined results.

   Invoke Editor
       Synopsis:

                     v

       Invoke an editor to edit the current file being examined. If
       standard input is being examined, the results are unspecified.
       The name of the editor shall be taken from the environment
       variable EDITOR, or shall default to vi.  If the last pathname
       component in EDITOR is either vi or ex, the editor shall be
       invoked with a -c linenumber command line argument, where
       linenumber is the line number of the file line containing the
       display line currently displayed as the first line of the screen.
       It is implementation-defined whether line-setting options are
       passed to editors other than vi and ex.

       When the editor exits, more shall resume with the same file and
       screen as when the editor was invoked.

   Display Position
       Synopsis:

                     =
                     <control>-G

       Write a message for which the information references the first
       byte of the line after the last line of the file on the screen.
       This message shall include the name of the file currently being
       examined, its number relative to the total number of files there
       are to examine, the line number in the file, the byte number and
       the total bytes in the file, and what percentage of the file
       precedes the current position. If more is reading from standard
       input, or the file is shorter than a single screen, the line
       number, the byte number, the total bytes, and the percentage need
       not be written.

   Quit
       Synopsis:

                     q
                     :q
                     ZZ

       Exit more.

EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS         top

       If an error is encountered accessing a file when using the :n
       command, more shall attempt to examine the next file in the
       argument list, but the final exit status shall be affected. If an
       error is encountered accessing a file via the :p command, more
       shall attempt to examine the previous file in the argument list,
       but the final exit status shall be affected. If an error is
       encountered accessing a file via the :e command, more shall
       remain in the current file and the final exit status shall not be
       affected.

       The following sections are informative.

APPLICATION USAGE         top

       When the standard output is not a terminal, only the -s filter-
       modification option is effective. This is based on historical
       practice. For example, a typical implementation of man pipes its
       output through more -s to squeeze excess white space for terminal
       users. When man is piped to lp, however, it is undesirable for
       this squeezing to happen.

EXAMPLES         top

       The -p allows arbitrary commands to be executed at the start of
       each file.  Examples are:

       more -p G file1 file2
             Examine each file starting with its last screenful.

       more -p 100 file1 file2
             Examine each file starting with line 100 in the current
             position (usually the third line, so line 98 would be the
             first line written).

       more -p /100 file1 file2
             Examine each file starting with the first line containing
             the string "100" in the current position

RATIONALE         top

       The more utility, available in BSD and BSD-derived systems, was
       chosen as the prototype for the POSIX file display program since
       it is more widely available than either the public-domain program
       less or than pg, a pager provided in System V. The 4.4 BSD more
       is the model for the features selected; it is almost fully
       upwards-compatible from the 4.3 BSD version in wide use and has
       become more amenable for vi users. Several features originally
       derived from various file editors, found in both less and pg,
       have been added to this volume of POSIX.1‐2017 as they have
       proved extremely popular with users.

       There are inconsistencies between more and vi that result from
       historical practice. For example, the single-character commands
       h, f, b, and <space> are screen movers in more, but cursor movers
       in vi.  These inconsistencies were maintained because the cursor
       movements are not applicable to more and the powerful
       functionality achieved without the use of the control key
       justifies the differences.

       The tags interface has been included in a program that is not a
       text editor because it promotes another degree of consistent
       operation with vi.  It is conceivable that the paging environment
       of more would be superior for browsing source code files in some
       circumstances.

       The operating mode referred to for block-mode terminals
       effectively adds a <newline> to each Synopsis line that currently
       has none. So, for example, d<newline> would page one screenful.
       The mode could be triggered by a command line option, environment
       variable, or some other method. The details are not imposed by
       this volume of POSIX.1‐2017 because there are so few systems
       known to support such terminals. Nevertheless, it was considered
       that all systems should be able to support more given the
       exception cited for this small community of terminals because, in
       comparison to vi, the cursor movements are few and the command
       set relatively amenable to the optional <newline> characters.

       Some versions of more provide a shell escaping mechanism similar
       to the ex !  command. The standard developers did not consider
       that this was necessary in a paginator, particularly given the
       wide acceptance of multiple window terminals and job control
       features. (They chose to retain such features in the editors and
       mailx because the shell interaction also gives an opportunity to
       modify the editing buffer, which is not applicable to more.)

       The -p (position) option replaces the + command because of the
       Utility Syntax Guidelines. The +command option is no longer
       specified by POSIX.1‐2008 but may be present in some
       implementations. In early proposals, it took a pattern argument,
       but historical less provided the more general facility of a
       command. It would have been desirable to use the same -c as ex
       and vi, but the letter was already in use.

       The text stating ``from a non-rewindable stream ...
       implementations may limit the amount of backwards motion
       supported'' would allow an implementation that permitted no
       backwards motion beyond text already on the screen. It was not
       possible to require a minimum amount of backwards motion that
       would be effective for all conceivable device types. The
       implementation should allow the user to back up as far as
       possible, within device and reasonable memory allocation
       constraints.

       Historically, non-printable characters were displayed using the
       ARPA standard mappings, which are as follows:

        1. Printable characters are left alone.

        2. Control characters less than \177 are represented as followed
           by the character offset from the '@' character in the ASCII
           map; for example, \007 is represented as 'G'.

        3. \177 is represented as followed by '?'.

       The display of characters having their eighth bit set was less
       standard. Existing implementations use hex (0x00), octal (\000),
       and a meta-bit display. (The latter displayed characters with
       their eighth bit set as the two characters "M-", followed by the
       seven-bit display as described previously.) The latter probably
       has the best claim to historical practice because it was used
       with the -v option of 4 BSD and 4 BSD-derived versions of the cat
       utility since 1980.

       No specific display format is required by POSIX.1‐2008.
       Implementations are encouraged to conform to historic practice in
       the absence of any strong reason to diverge.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Chapter 2, Shell Command Language, ctags(1p), ed(1p), ex(1p),
       vi(1p)

       The Base Definitions volume of POSIX.1‐2017, Chapter 8,
       Environment Variables, Section 9.2, Regular Expression General
       Requirements, Section 9.3, Basic Regular Expressions, Section
       12.2, Utility Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                          MORE(1P)

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