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PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
FC(1P) POSIX Programmer's Manual FC(1P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
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 command.
The fc utility shall conform to the Base Definitions volume of
POSIX.1‐2008, 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
POSIX.1‐2008, 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.
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 <equals-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.
Not used.
None.
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 POSIX.1‐2008, 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.
Default.
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>
The standard error shall be used only for diagnostic messages.
None.
None.
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.
Default.
The following sections are informative.
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$$
None.
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.
None.
sh(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 FC(1P)
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