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fc(1)									 fc(1)

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 lists or edits and reexecutes, commands previously entered
     to an interactive sh.

     The command history list references commands by number. The first number
     in the list is selected arbitrarily.  The relationship of a number to its
     command will 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-dependent upper limit, which will 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 will 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 will be entered at the end of the history list and then
     reexecuted by sh. The fc command that caused the editing will not be
     entered into the history list. If the editor returns a non-zero exit
     status, this will suppress the entry into the history list and the
     command reexecution. Any command-line variable assignments or redirection
     operators used with fc will 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 supports the XBD specification, Utility Syntax Guidelines.

     The following options are 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.	 The value in the FCEDIT variable is used as a
		 default when -e is not specified. If FCEDIT is null or unset,
		 ed will be used as the editor.

									Page 1

fc(1)									 fc(1)

     -l		 (The letter ell.) List the commands rather than invoking an
		 editor on them. The commands will 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		 Reexecute the command without invoking an editor.

OPERANDS
     The following operands are supported:

     first

     last	 Select the commands to list or edit. The number of previous
		 commands that can be accessed is determined by the value of
		 the HISTSIZE variable. The value of first or last or both
		 will 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 will be used.

		 For the synopsis forms without -s:

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

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

									Page 2

fc(1)									 fc(1)

		     If first and last are both present, all of the commands
		     from first to last will be edited (without -l) or listed
		     (with -l). Editing multiple commands will 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 will
		     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 will not be an error
		     to specify first or last values that are not in the
		     history list; fc will 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

		     will list and edit, respectively, all ten commands.

     old=new	 Replace the first occurrence of string old in the commands to
		 be reexecuted by the string new.

ENVIRONMENT VARIABLES
     The following environment variables affect the execution of fc:

     FCEDIT	 This variable, when expanded by the shell, determines the
		 default value for the -e editor option's editor option-
		 argument. If FCEDIT is null or unset, ed will 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 user's home directory. If
		 the shell cannot obtain both read and write access to, or
		 create, the history file, it will use an unspecified
		 mechanism that allows the history to operate properly.
		 (References to history "file" in this section are understood
		 to mean this unspecified mechanism in such cases.) An
		 implementation may choose to access this variable only when
		 initialising the history file; this initialisation will 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-
		 dependent system startup files. (The initialisation process

									Page 3

fc(1)									 fc(1)

		 for the history file can be dependent on the system startup
		 files, in that they may contain commands that will
		 effectively preempt the user's settings of HISTFILE and
		 HISTSIZE. For example, function definition commands are
		 recorded in the history file, unless the set -o nolog option
		 is set. If the system administrator includes function
		 definitions in some system startup file called before the ENV
		 file, the history file will be initialised before the user
		 gets a chance to influence its characteristics.) In some
		 historical shells, the history file is initialised just after
		 the ENV file has been processed.  Therefore, it is
		 implementation-dependent whether changes made to HISTFILE
		 after the history file has been initialised 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
		 will occur are implementation-dependent. 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
		 will 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 will be used. The maximum number of commands in
		 the history list is unspecified, but will be at least 128. An
		 implementation may choose to access this variable only when
		 initialising the history file, as described under HISTFILE
		 Therefore, it is unspecified whether changes made to HISTSIZE
		 after the history file has been initialised are effective.

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

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

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

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

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

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

									Page 4

fc(1)									 fc(1)

EXIT STATUS
     The following exit values are returned:

     0	 Successful completion of the listing.

     >0	 An error occurred.

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

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

     will 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$$

SEE ALSO
     sh(1).

									Page 5

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