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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 |
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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.1‐2017, 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.1‐2017, 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.1‐2017, 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.1‐2017, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 original Standard can be obtained online at
http://www.opengroup.org/unix/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 2017 FC(1P)
Pages that refer to this page: sh(1p)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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