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fc command in ksh shell

The internal fc command provides access to your history file. The Korn shell creates a history file containing the commands you have previously entered during your current login session. You use the fc utility to:

* Display the contents of the history file.

* Edit (Visually) the contents of the history file.

* Reexecute previous commands stored in the history file.

Following is the general format of the ksh version of fc command.

     fc      [ -e editor ] [ -lnr ] [ first [ last ] ]
     fc -e - [ old=new ]   [ command ]

history is an alias for fc -l

r is an alias for fc -e -.

The r command is called the repeat command. It searches for a string in the history file that matches the given argument and then executes the entire line in which the string was found.

Options

The following list describes the options and their arguments that may be used to control how fc functions.

First format
-e editor	Use editor editor to edit the commands in the history file. The editing of the history file is referred to as in-line command editing. If you do not specify the -e option, fc checks the value of the FCEDIT variable for an editor name. If FCEDIT is not defined then /bin/ed is used. Valid editors are vi, emacs, gmacs, and ed.
-l	List the contents of the history file.
-n	Suppress the command numbers when displaying the commands from the history file.
-r	Reverse the order of the commands in the history file when they are listed.
-first	Beginning command. The number of lines to go back from the last command to start listing out the history file. For example,

                     fc -l -25 # last 25 commands
                     history -25

-last

Ending command. The number of lines to go back from the last command to end listing out the history file. For example,

                     fc -l -n -25 -5 # 25 commands ago down to 5 commands ago
                     history -n -25 -5

Second Format
-e -	Reexecutes the previous command in the history file. If you do not specify a command or partial command, then the last command you executed is re- executed. This command is the r alias (alias r="fc -e -").

Arguments

The following list describes the arguments that may be passed to the fc command.

First Format
first	List commands starting at line first in the history file. For instance,

                     fc -l 1 # list all commands (starting from line 1
                     history 1

last

List commands up to line last in the history file. For example,

                     fc -l 20 30
                      history 20 30

displays lines 20 through 30 of the history file.

Second Format
old=new	Substitutes old string for new string in the appropriate command before reexecuting it.
command	The command to reexecute from the history file. Command may be one of the following:

* Positive number denoting the event number associated with a command.

* Negative number subtracted from the current command number. The event number of the subtraction is executed.

* A string. The latest command starting with the string is executed. For instance,

            fc -e c
or

            r c

searches the history file for the last command that began with a c.

* If no command is specified then the previous command is executed.

Variables

There are two variables that control the location and size of the history file. The HISTFILE variable informs the shell where to locate the history file. For example,

     HISTFILE=$HOME/.history

places the history file in your HOME directory in the .history file. If you do not specify a path in the HISTFILE variable, the default for the location is $HOME/.sh_history.

The HISTSIZE variable is used to set the number of commands that are stored in the history file. If you do not set the HISTSIZE variable to some number it defaults to 128. Therefore, the history file will contain the last 128 commands you have entered.

The FCEDIT variable is used to define the editor used to edit your history file. The possible editors are vi, emacs, gmacs, and ed.

/usr/bin/fc [first[last]]
/usr/bin/fc -l [-nr] [first[last]]
/usr/bin/fc -s [old=new] [first]

ksh

fc -e - [old=new] [command]
fc [-e ename] [-nlr] [first[last]]

/usr/bin/fc

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 the value in HISTSIZE or 128 (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 32 766, 32 767, 1 (wrapped), and 2 as they are executed, command 32 767 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.

History Substitution

History substitution allows you to use words from previous command lines in the command line you are typing. This simplifies spelling corrections and the repetition of complicated commands or arguments. Command lines are saved in the history list, the size of which is controlled by the history variable. The history shell variable may be set to the maximum number of command lines that will be saved in the history file; i.e.:

set history = 200

will allow the history list to keep track of the most recent 200 command lines. If not set, the C shell saves only the most recent command.

A history substitution begins with a ! (although you can change this with the histchars variable) and may occur anywhere on the command line; history substitutions do not nest. The ! can be escaped with \ to suppress its special meaning.

Input lines containing history substitutions are echoed on the terminal after being expanded, but before any other substitutions take place or the command gets executed.

ksh

Using fc, in the form of

fc -e - [ old=new ] [ command ],

the command is re-executed after the substitution old=new is performed. If there is not a command argument, the most recent command typed at this terminal is executed.

Using fc in the form of

fc [ -e ename ] [ -nlr ] [ first [ last ] ],

a range of commands from first to last is selected from the last HISTSIZE commands that were typed at the terminal. The arguments first and last may be specified as a number or as a string. A string is used to locate the most recent command starting with the given string. A negative number is used as an offset to the current command number. If the -l flag is selected, the commands are listed on standard output. Otherwise, the editor program -e name is invoked on a file containing these keyboard commands. If ename is not supplied, then the value of the variable FCEDIT (default /bin/ed) is used as the editor. When editing is complete, the edited command(s) is executed. If last is not specified then it will be set to first. If first is not specified the default is the previous command for editing and -16 for listing. The flag -r reverses the order of the commands and the flag -n suppresses command numbers when listing. (See ksh(1) for more about command line editing.)

HISTFILE: If this variable is set when the shell is invoked, then the value is the pathname of the file that will be used to store the command history.
HISTSIZE: If this variable is set when the shell is invoked, then the number of previously entered commands that are accessible by this shell will be greater than or equal to this number. The default is 128.

Command Re-entry:

The text of the last HISTSIZE (default 128) commands entered from a terminal device is saved in a history file. The file $HOME/.sh_history is used if the HISTFILE variable is not set or if the file it names is not writable. A shell can access the commands of all interactive shells which use the same named HISTFILE. The special command fc is used to list or edit a portion of this file. The portion of the file to be edited or listed can be selected by number or by giving the first character or characters of the command. A single command or range of commands can be specified. If you do not specify an editor program as an argument to fc then the value of the variable FCEDIT is used. If FCEDIT is not defined then /bin/ed is used. The edited command(s) is printed and re-executed upon leaving the editor. The editor name - is used to skip the editing phase and to re-execute the command. In this case a substitution parameter of the form old=new can be used to modify the command before execution. For example, if r is aliased to ´fc -e - ´ then typing `r bad=good c' will re-execute the most recent command which starts with the letter c, replacing the first occurrence of the string bad with the string good.

Using the fc built-in command within a compound command will cause the whole command to disappear from the history file.

OPTIONS

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.
-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: Re-execute 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).
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.

OUTPUT

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 commandcommand consists of more than one line, the lines after the first are displayed as:

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

EXAMPLES

Example 1 Using `history` and `fc`

             csh                                     ksh

% history                               $ fc -l
  1   cd /etc                             1   cd /etc
  2   vi passwd                           2   vi passwd
  3   date                                3   date
  4   cd                                  4   cd
  5   du .                                5   du .
  6   ls -t                               6   ls -t
  7   history                             7   fc -l

% !d                                    $ fc -e - d
  du .                                    du .
  262   ./SCCS                            262   ./SCCS
  336   .                                 336   .

% !da                                   $ fc -e - da
  Thu Jul 21 17:29:56 PDT 1994            Thu Jul 21 17:29:56 PDT 1994

%                                       $ alias \!='fc -e -'

% !!                                    $ !
  date                                    alias ='fc -e -'
  Thu Jul 21 17:29:56 PDT 1994

ENVIRONMENT VARIABLES

See environ(5) for descriptions of the following environment variables that affect the execution of fc: LC_CTYPE, LC_MESSAGES, and NLSPATH.

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.) fc may choose to access this variable only when initializing the history file; this initialization 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 a system startup file such as /etc/profile. (The initialization process 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 initialized before the user gets a chance to influence its characteristics.) The variable HISTFILE is accessed initially when the shell is invoked. Any changes to HISTFILE will not take effect until another shell is invoked.
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 variable HISTSIZE is accessed initially when the shell is invoked. Any changes to HISTSIZE will not take effect until another shell is invoked.

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.

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Last modified: February 28, 2008