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 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.

Display the history list; if n is given, display only the n most recent events.

-r

Reverse the order of printout to be most recent first rather than oldest first.

-h

Display the history list without leading numbers. This is used to produce files suitable for sourcing using the -h option to the csh built-in command, source(1).

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.

An event designator is a reference to a command line entry in the history list.

!

Start a history substitution, except when followed by a space character, tab, newline, = or (.

!!

Refer to the previous command. By itself, this substitution repeats the previous command.

!n

Refer to command line n.

!-n

Refer to the current command line minus n.

!str

Refer to the most recent command starting with str.

!?str?

Refer to the most recent command containing str.

!?str? additional

Refer to the most recent command containing str and append additional to that referenced command.

!{command} additional

Refer to the most recent command beginning with command and append additional to that referenced command.

^previous_word^replacement^

Repeat the previous command line replacing the string previous_word with the string replacement. This is equivalent to the history substitution:

!:s/previous_word/replacement/.

To re-execute a specific previous command AND make such a substitution, say, re-executing command #6,

!:6s/previous_word/replacement/.

A `:' (colon) separates the event specification from the word designator. 2It can be omitted if the word designator begins with a ^, $, *, - or %. If the word is to be selected from the previous command, the second ! character can be omitted from the event specification. For instance, !!:1 and !:1 both refer to the first word of the previous command, while !!$ and !$ both refer to the last word in the previous command. Word designators include:

#

The entire command line typed so far.

0

The first input word (command).

n

The n'th argument.

^

The first argument, that is, 1.

$

The last argument.

%

The word matched by (the most recent) ?s search.

x-y

A range of words; -y abbreviates 0-y.

*

All the arguments, or a null value if there is just one word in the event.

x*

Abbreviates x-$.

x-

Like x* but omitting word $.

After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a :.

h

Remove a trailing pathname component, leaving the head.

r

Remove a trailing suffix of the form `.xxx', leaving the basename.

e

Remove all but the suffix, leaving the extension.

s/oldchars/replacements/ Substitute

replacements for oldchars. oldchars is a string that may contain embedded blank spaces, whereas previous_word in the event designator

^oldchars^replacements^

may not.

t

Remove all leading pathname components, leaving the tail.

&

Repeat the previous substitution.

g

Apply the change to the first occurrence of a match in each word, by prefixing the above (for example, g&).

p

Print the new command but do not execute it.

q

Quote the substituted words, escaping further substitutions.

x

Like q, but break into words at each space character, tab or newline.

Unless preceded by a g, the modification is applied only to the first string that matches oldchars; an error results if no string matches.

The left-hand side of substitutions are not regular expressions, but character strings. Any character can be used as the delimiter in place of /. A backslash quotes the delimiter character. The character &, in the right hand side, is replaced by the text from the left-hand-side. The & can be quoted with a backslash. A null oldchars uses the previous string either from a oldchars or from a contextual scan string s from !?s. You can omit the rightmost delimiter if a newline immediately follows replacements; the rightmost ? in a context scan can similarly be omitted.

Without an event specification, a history reference refers either to the previous command, or to a previous history reference on the command line (if any).

Using fc, in the form of

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

Using fc in the form of

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

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.

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.

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