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NAME

       fc - process the command history list

SYNOPSIS

       fc [-r][-e editor] [first[last]]

       fc -l[-nr] [first[last]]

       fc -s[old=new][first]

DESCRIPTION

       The  fc  utility  shall  list,  or  shall edit and re-execute, commands
       previously entered to an interactive sh.

       The command history list shall reference commands by number. The  first
       number  in  the  list  is  selected  arbitrarily. The relationship of a
       number to its command shall not change except when the user logs in and
       no  other  process  is accessing the list, at which time the system may
       reset the numbering to start the oldest  retained  command  at  another
       number  (usually  1). When the number reaches an implementation-defined
       upper limit, which shall be no smaller than the value  in  HISTSIZE  or
       32767  (whichever is greater), the shell may wrap the numbers, starting
       the next command with a lower number (usually 1). However, despite this
       optional  wrapping  of  numbers,  fc  shall  maintain the time-ordering
       sequence of the commands. For example, if four commands in sequence are
       given  the  numbers  32766,  32767,  1  (wrapped),  and  2  as they are
       executed, command 32767 is considered the command previous to  1,  even
       though its number is higher.

       When  commands  are  edited  (when the -l option is not specified), the
       resulting lines shall be entered at the end of  the  history  list  and
       then  re-executed  by  sh. The fc command that caused the editing shall
       not be entered into the history list. If the editor returns a  non-zero
       exit  status,  this  shall suppress the entry into the history list and
       the command re-execution. Any  command  line  variable  assignments  or
       redirection  operators  used  with  fc shall affect both the fc command
       itself as well as the command that results; for example:

              fc -s -- -1 2>/dev/null

       reinvokes the previous command, suppressing standard error for both  fc
       and the previous command.

OPTIONS

       The  fc  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:

       -e  editor
              Use the editor named by editor to edit the commands. The  editor
              string  is  a  utility  name,  subject  to  search  via the PATH
              variable    (see    the    Base    Definitions     volume     of
              IEEE Std 1003.1-2001,  Chapter  8,  Environment  Variables). The
              value in the FCEDIT variable shall be used as a default when  -e
              is  not  specified. If FCEDIT is null or unset, ed shall be used
              as the editor.

       -l     (The letter ell.) List the  commands  rather  than  invoking  an
              editor  on  them.  The commands shall be written in the sequence
              indicated by the first and last operands,  as  affected  by  -r,
              with each command preceded by the command number.

       -n     Suppress command numbers when listing with -l.

       -r     Reverse  the  order  of  the commands listed (with -l) or edited
              (with neither -l nor -s).

       -s     Re-execute the command without invoking an editor.

OPERANDS

       The following operands shall be supported:

       first, last
              Select the commands to list or  edit.  The  number  of  previous
              commands  that  can be accessed shall be determined by the value
              of the HISTSIZE variable. The value of first  or  last  or  both
              shall be one of the following:

       [+]number
              A positive number representing a command number; command numbers
              can be displayed with the -l option.

       -number
              A negative decimal number  representing  the  command  that  was
              executed  number  of commands previously. For example, -1 is the
              immediately previous command.

       string
              A string indicating  the  most  recently  entered  command  that
              begins  with  that  string.  If the old= new operand is not also
              specified with -s, the string form of the first  operand  cannot
              contain an embedded equal sign.

       When the synopsis form with -s is used:

               * If first is omitted, the previous command shall be used.

       For the synopsis forms without -s:

               * If  last  is  omitted,  last  shall  default  to the previous
                 command when -l is specified; otherwise, it shall default  to
                 first.

               * If  first and last are both omitted, the previous 16 commands
                 shall be listed or  the  previous  single  command  shall  be
                 edited (based on the -l option).

               * If  first and last are both present, all of the commands from
                 first to last shall be edited (without -l)  or  listed  (with
                 -l).  Editing  multiple  commands  shall  be  accomplished by
                 presenting to the editor all of the  commands  at  one  time,
                 each  command  starting  on a new line. If first represents a
                 newer command than last, the  commands  shall  be  listed  or
                 edited  in  reverse  sequence,  equivalent  to  using -r. For
                 example,  the  following  commands  on  the  first  line  are
                 equivalent to the corresponding commands on the second:

                 fc -r 10 20    fc    30 40
                 fc    20 10    fc -r 40 30

               * When a range of commands is used, it shall not be an error to
                 specify first or last values that  are  not  in  the  history
                 list;  fc  shall substitute the value representing the oldest
                 or newest command in the list, as appropriate.  For  example,
                 if  there are only ten commands in the history list, numbered
                 1 to 10:

                 fc -l
                 fc 1 99

              shall list and edit, respectively, all ten commands.

       old=new
              Replace the first occurrence of string old in the commands to be
              re-executed by the string new.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of fc:

       FCEDIT This  variable,  when expanded by the shell, shall determine the
              default value for the -e editor option’s editor option-argument.
              If FCEDIT is null or unset, ed shall be used as the editor.

       HISTFILE
              Determine  a  pathname  naming  a  command  history file. If the
              HISTFILE variable is not set, the shell may attempt to access or
              create  a  file  .sh_history in the directory referred to by the
              HOME environment variable. If the shell cannot obtain both  read
              and  write  access to, or create, the history file, it shall use
              an unspecified mechanism that  allows  the  history  to  operate
              properly. (References to history "file" in this section shall be
              understood to mean this unspecified mechanism in such cases.) An
              implementation  may  choose  to  access  this variable only when
              initializing the history file; this initialization  shall  occur
              when  fc  or  sh  first attempt to retrieve entries from, or add
              entries to, the file, as the result of commands  issued  by  the
              user,  the  file  named  by the ENV variable, or implementation-
              defined system start-up files. In some  historical  shells,  the
              history  file  is  initialized  just after the ENV file has been
              processed.   Therefore,  it  is  implementation-defined  whether
              changes  made  to  HISTFILE  after  the  history  file  has been
              initialized are effective. Implementations may choose to disable
              the history list mechanism for users with appropriate privileges
              who do not set HISTFILE ; the specific circumstances under which
              this   occurs  are  implementation-defined.  If  more  than  one
              instance of the shell is using the  same  history  file,  it  is
              unspecified  how  updates  to the history file from those shells
              interact. As entries are deleted from  the  history  file,  they
              shall  be  deleted oldest first.  It is unspecified when history
              file entries are physically removed from the history file.

       HISTSIZE
              Determine a decimal number representing the limit to the  number
              of  previous  commands  that are accessible. If this variable is
              unset, an unspecified default greater than or equal to 128 shall
              be  used.  The maximum number of commands in the history list is
              unspecified, but shall be at least 128.  An  implementation  may
              choose  to  access  this  variable  only  when  initializing the
              history file, as described under HISTFILE  .  Therefore,  it  is
              unspecified  whether  changes made to HISTSIZE after the history
              file has been initialized are effective.

       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).

       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

       When the -l option is used to list commands, the format of each command
       in the list shall be as follows:

              "%d\t%s\n", <line number>, <command>

       If both the -l and -n options are specified, the format of each command
       shall be:

              "\t%s\n", <command>

       If the <command> consists of more than one line, the  lines  after  the
       first shall be displayed as:

              "\t%s\n", <continued-command>

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     Successful completion of the listing.

       >0     An error occurred.

       Otherwise,  the  exit  status shall be that of the commands executed by
       fc.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       Since editors sometimes use file descriptors as integral parts of their
       editing,  redirecting  their file descriptors as part of the fc command
       can produce unexpected results.  For  example,  if  vi  is  the  FCEDIT
       editor, the command:

              fc -s | more

       does not work correctly on many systems.

       Users  on windowing systems may want to have separate history files for
       each window by setting HISTFILE as follows:

              HISTFILE=$HOME/.sh_hist$$

EXAMPLES

       None.

RATIONALE

       This utility is based on the fc built-in of the KornShell.

       An early proposal specified the -e option as [-e editor [ old = new ]],
       which  is  not historical practice. Historical practice in fc of either
       [-e editor ] or [-e - [ old =  new  ]]  is  acceptable,  but  not  both
       together.   To  clarify  this, a new option -s was introduced replacing
       the [-e -]. This resolves the conflict and  makes  fc  conform  to  the
       Utility Syntax Guidelines.

       HISTFILE
              Some  implementations  of  the KornShell check for the superuser
              and do not create a history file unless HISTFILE is  set.   This
              is  done  primarily to avoid creating unlinked files in the root
              file system when logging in during single-user  mode.   HISTFILE
              must be set for the superuser to have history.

       HISTSIZE
              Needed  to  limit the size of history files. It is the intent of
              the standard developers that when  two  shells  share  the  same
              history  file,  commands  that are entered in one shell shall be
              accessible by the other shell. Because of  the  difficulties  of
              synchronization   over  a  network,  the  exact  nature  of  the
              interaction is unspecified.

       The initialization process for the history file can be dependent on the
       system   start-up  files,  in  that  they  may  contain  commands  that
       effectively preempt the settings the user has for HISTFILE and HISTSIZE
       . For example, function definition commands are recorded in the history
       file. If the system administrator includes function definitions in some
       system  start-up  file  called before the ENV file, the history file is
       initialized before the user can influence its characteristics. In  some
       historical  shells,  the history file is initialized just after the ENV
       file has been processed. Because of these situations, the text requires
       the initialization process to be implementation-defined.

       Consideration  was  given  to  omitting  the fc utility in favor of the
       command line editing feature in sh. For example, in  vi  editing  mode,
       typing "<ESC> v" is equivalent to:

              EDITOR=vi fc

       However,  the  fc  utility  allows  the  user  the  flexibility to edit
       multiple commands simultaneously (such as fc 10 20) and to use  editors
       other than those supported by sh for command line editing.

       In  the  KornShell,  the  alias  r  (‘‘re-do")  is  preset  to  fc -e -
       (equivalent to the POSIX fc -s). This is  probably  an  easier  command
       name  to  remember  than  fc (‘‘fix command"), but it does not meet the
       Utility Syntax Guidelines. Renaming fc to hist or redo was  considered,
       but   since  this  description  closely  matches  historical  KornShell
       practice already, such a renaming was seen  as  gratuitous.  Users  are
       free  to  create aliases whenever odd historical names such as fc, awk,
       cat, grep, or yacc are standardized by POSIX.

       Command numbers have no ordering effects; they are like serial numbers.
       The  -r  option  and  -number  operand  address the sequence of command
       execution, regardless of  serial  numbers.  So,  for  example,  if  the
       command  number  wrapped back to 1 at some arbitrary point, there would
       be no ambiguity associated with traversing the wrap point. For example,
       if the command history were:

              32766: echo 1
              32767: echo 2
              1: echo 3

       the number -2 refers to command 32767 because it is the second previous
       command, regardless of serial number.

FUTURE DIRECTIONS

       None.

SEE ALSO

       sh

COPYRIGHT

       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- 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 .