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Linux 2.6 - man page for fc (linux section 1posix)

FC(P)				    POSIX Programmer's Manual				    FC(P)

       fc - process the command history list

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

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

       fc -s[old=new][first]

       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

       The fc utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001,  Sec-
       tion 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     Re-execute the command without invoking an editor.

       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:

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

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

	      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 speci-
		 fied; 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 rep-
		 resenting 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.

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

       Not used.


       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.

	      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 mech-
	      anism 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  initial-
	      ized  are  effective. Implementations may choose to disable the history list mecha-
	      nism 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.

	      Determine  a  decimal  number representing the limit to the number of previous com-
	      mands 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, Inter-
	      nationalization 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  interna-
	      tionalization variables.

	      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  argu-
	      ments and input files).

	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error.

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


       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 dis-
       played as:

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

       The standard error shall be used only for diagnostic messages.



       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.


       The following sections are informative.

       Since editors sometimes use file descriptors as integral parts of their editing, redirect-
       ing  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 set-
       ting HISTFILE as follows:



       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 his-
       torical 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  Syn-
       tax Guidelines.

	      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.

	      Needed to limit the size of history files. It is the intent of the standard  devel-
	      opers  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 initial-
       ized  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 simulta-
       neously (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 com-
       mand 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,  regard-
       less of serial number.



       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					    FC(P)

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