1FC(1P) POSIX Programmer's Manual FC(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 fc — process the command history list
13
15 fc [-r] [-e editor] [first [last]]
16 fc -l [-nr] [first [last]]
18 fc -s [old=new] [first]
20
22 The fc utility shall list, or shall edit and re-execute, commands pre‐
23 viously entered to an interactive sh.
24 The command history list shall reference commands by number. The first
26 number in the list is selected arbitrarily. The relationship of a num‐
27 ber to its command shall not change except when the user logs in and no
28 other process is accessing the list, at which time the system may reset
29 the numbering to start the oldest retained command at another number
30 (usually 1). When the number reaches an implementation-defined upper
31 limit, which shall be no smaller than the value in HISTSIZE or 32767
32 (whichever is greater), the shell may wrap the numbers, starting the
33 next command with a lower number (usually 1). However, despite this
34 optional wrapping of numbers, fc shall maintain the time-ordering
35 sequence of the commands. For example, if four commands in sequence are
36 given the numbers 32766, 32767, 1 (wrapped), and 2 as they are exe‐
37 cuted, command 32767 is considered the command previous to 1, even
38 though its number is higher.
39 When commands are edited (when the -l option is not specified), the
41 resulting lines shall be entered at the end of the history list and
42 then re-executed by sh. The fc command that caused the editing shall
43 not be entered into the history list. If the editor returns a non-zero
44 exit status, this shall suppress the entry into the history list and
45 the command re-execution. Any command line variable assignments or re‐
46 direction operators used with fc shall affect both the fc command
47 itself as well as the command that results; for example:
48 fc -s -- -1 2>/dev/null
51 reinvokes the previous command, suppressing standard error for both fc
53 and the previous command.
54
56 The fc utility shall conform to the Base Definitions volume of
57 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
58 The following options shall be supported:
60 -e editor Use the editor named by editor to edit the commands. The edi‐
62 tor string is a utility name, subject to search via the PATH
63 variable (see the Base Definitions volume of POSIX.1‐2017,
64 Chapter 8, Environment Variables). The value in the FCEDIT
65 variable shall be used as a default when -e is not specified.
66 If FCEDIT is null or unset, ed shall be used as the editor.
67 -l (The letter ell.) List the commands rather than invoking an
69 editor on them. The commands shall be written in the sequence
70 indicated by the first and last operands, as affected by -r,
71 with each command preceded by the command number.
72 -n Suppress command numbers when listing with -l.
74 -r Reverse the order of the commands listed (with -l) or edited
76 (with neither -l nor -s).
77 -s Re-execute the command without invoking an editor.
79
81 The following operands shall be supported:
82 first, last
84 Select the commands to list or edit. The number of previous
85 commands that can be accessed shall be determined by the
86 value of the HISTSIZE variable. The value of first or last or
87 both shall be one of the following:
88 [+]number A positive number representing a command number;
90 command numbers can be displayed with the -l
91 option.
92 -number A negative decimal number representing the command
94 that was executed number of commands previously.
95 For example, -1 is the immediately previous com‐
96 mand.
97 string A string indicating the most recently entered com‐
99 mand that begins with that string. If the old=new
100 operand is not also specified with -s, the string
101 form of the first operand cannot contain an embed‐
102 ded <equals-sign>.
103 When the synopsis form with -s is used:
105 * If first is omitted, the previous command shall be used.
107 For the synopsis forms without -s:
109 * If last is omitted, last shall default to the previous
111 command when -l is specified; otherwise, it shall default
112 to first.
113 * If first and last are both omitted, the previous 16 com‐
115 mands shall be listed or the previous single command
116 shall be edited (based on the -l option).
117 * If first and last are both present, all of the commands
119 from first to last shall be edited (without -l) or listed
120 (with -l). Editing multiple commands shall be accom‐
121 plished by presenting to the editor all of the commands
122 at one time, each command starting on a new line. If
123 first represents a newer command than last, the commands
124 shall be listed or edited in reverse sequence, equivalent
125 to using -r. For example, the following commands on the
126 first line are equivalent to the corresponding commands
127 on the second:
128 fc -r 10 20 fc 30 40
131 fc 20 10 fc -r 40 30
132 * When a range of commands is used, it shall not be an
134 error to specify first or last values that are not in the
135 history list; fc shall substitute the value representing
136 the oldest or newest command in the list, as appropriate.
137 For example, if there are only ten commands in the his‐
138 tory list, numbered 1 to 10:
139 fc -l
142 fc 1 99
143 shall list and edit, respectively, all ten commands.
145 old=new Replace the first occurrence of string old in the commands to
147 be re-executed by the string new.
148
150 Not used.
151
153 None.
154
156 The following environment variables shall affect the execution of fc:
157 FCEDIT This variable, when expanded by the shell, shall determine
159 the default value for the -e editor option's editor option-
160 argument. If FCEDIT is null or unset, ed shall be used as the
161 editor.
162 HISTFILE Determine a pathname naming a command history file. If the
164 HISTFILE variable is not set, the shell may attempt to access
165 or create a file .sh_history in the directory referred to by
166 the HOME environment variable. If the shell cannot obtain
167 both read and write access to, or create, the history file,
168 it shall use an unspecified mechanism that allows the history
169 to operate properly. (References to history ``file'' in this
170 section shall be understood to mean this unspecified mecha‐
171 nism in such cases.) An implementation may choose to access
172 this variable only when initializing the history file; this
173 initialization shall occur when fc or sh first attempt to
174 retrieve entries from, or add entries to, the file, as the
175 result of commands issued by the user, the file named by the
176 ENV variable, or implementation-defined system start-up
177 files. In some historical shells, the history file is ini‐
178 tialized just after the ENV file has been processed. There‐
179 fore, it is implementation-defined whether changes made to
180 HISTFILE after the history file has been initialized are
181 effective. Implementations may choose to disable the history
182 list mechanism for users with appropriate privileges who do
183 not set HISTFILE; the specific circumstances under which this
184 occurs are implementation-defined. If more than one instance
185 of the shell is using the same history file, it is unspeci‐
186 fied how updates to the history file from those shells inter‐
187 act. As entries are deleted from the history file, they shall
188 be deleted oldest first. It is unspecified when history file
189 entries are physically removed from the history file.
190 HISTSIZE Determine a decimal number representing the limit to the num‐
192 ber of previous commands that are accessible. If this vari‐
193 able is unset, an unspecified default greater than or equal
194 to 128 shall be used. The maximum number of commands in the
195 history list is unspecified, but shall be at least 128. An
196 implementation may choose to access this variable only when
197 initializing the history file, as described under HISTFILE.
198 Therefore, it is unspecified whether changes made to HISTSIZE
199 after the history file has been initialized are effective.
200 LANG Provide a default value for the internationalization vari‐
202 ables that are unset or null. (See the Base Definitions vol‐
203 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
204 ables for the precedence of internationalization variables
205 used to determine the values of locale categories.)
206 LC_ALL If set to a non-empty string value, override the values of
208 all the other internationalization variables.
209 LC_CTYPE Determine the locale for the interpretation of sequences of
211 bytes of text data as characters (for example, single-byte as
212 opposed to multi-byte characters in arguments and input
213 files).
214 LC_MESSAGES
216 Determine the locale that should be used to affect the format
217 and contents of diagnostic messages written to standard
218 error.
219 NLSPATH Determine the location of message catalogs for the processing
221 of LC_MESSAGES.
222
224 Default.
225
227 When the -l option is used to list commands, the format of each command
228 in the list shall be as follows:
229 "%d\t%s\n", <line number>, <command>
232 If both the -l and -n options are specified, the format of each command
234 shall be:
235 "\t%s\n", <command>
238 If the <command> consists of more than one line, the lines after the
240 first shall be displayed as:
241 "\t%s\n", <continued-command>
244
246 The standard error shall be used only for diagnostic messages.
247
249 None.
250
252 None.
253
255 The following exit values shall be returned:
256 0 Successful completion of the listing.
258 >0 An error occurred.
260 Otherwise, the exit status shall be that of the commands executed by
262 fc.
263
265 Default.
266 The following sections are informative.
268
270 Since editors sometimes use file descriptors as integral parts of their
271 editing, redirecting their file descriptors as part of the fc command
272 can produce unexpected results. For example, if vi is the FCEDIT edi‐
273 tor, the command:
274 fc -s | more
277 does not work correctly on many systems.
279 Users on windowing systems may want to have separate history files for
281 each window by setting HISTFILE as follows:
282 HISTFILE=$HOME/.sh_hist$$
285
287 None.
288
290 This utility is based on the fc built-in of the KornShell.
291 An early proposal specified the -e option as [-e editor [old= new ]],
293 which is not historical practice. Historical practice in fc of either
294 [-e editor] or [-e - [ old= new ]] is acceptable, but not both
295 together. To clarify this, a new option -s was introduced replacing the
296 [-e -]. This resolves the conflict and makes fc conform to the Utility
297 Syntax Guidelines.
298 HISTFILE Some implementations of the KornShell check for the superuser
300 and do not create a history file unless HISTFILE is set. This
301 is done primarily to avoid creating unlinked files in the
302 root file system when logging in during single-user mode.
303 HISTFILE must be set for the superuser to have history.
304 HISTSIZE Needed to limit the size of history files. It is the intent
306 of the standard developers that when two shells share the
307 same history file, commands that are entered in one shell
308 shall be accessible by the other shell. Because of the diffi‐
309 culties of synchronization over a network, the exact nature
310 of the interaction is unspecified.
311 The initialization process for the history file can be dependent on the
313 system start-up files, in that they may contain commands that effec‐
314 tively preempt the settings the user has for HISTFILE and HISTSIZE.
315 For example, function definition commands are recorded in the history
316 file. If the system administrator includes function definitions in some
317 system start-up file called before the ENV file, the history file is
318 initialized before the user can influence its characteristics. In some
319 historical shells, the history file is initialized just after the ENV
320 file has been processed. Because of these situations, the text requires
321 the initialization process to be implementation-defined.
322 Consideration was given to omitting the fc utility in favor of the com‐
324 mand line editing feature in sh. For example, in vi editing mode, typ‐
325 ing "<ESC>v" is equivalent to:
326 EDITOR=vi fc
329 However, the fc utility allows the user the flexibility to edit multi‐
331 ple commands simultaneously (such as fc 10 20) and to use editors other
332 than those supported by sh for command line editing.
333 In the KornShell, the alias r (``re-do'') is preset to fc -e - (equiva‐
335 lent to the POSIX fc -s). This is probably an easier command name to
336 remember than fc (``fix command''), but it does not meet the Utility
337 Syntax Guidelines. Renaming fc to hist or redo was considered, but
338 since this description closely matches historical KornShell practice
339 already, such a renaming was seen as gratuitous. Users are free to
340 create aliases whenever odd historical names such as fc, awk, cat,
341 grep, or yacc are standardized by POSIX.
342 Command numbers have no ordering effects; they are like serial numbers.
344 The -r option and -number operand address the sequence of command exe‐
345 cution, regardless of serial numbers. So, for example, if the command
346 number wrapped back to 1 at some arbitrary point, there would be no
347 ambiguity associated with traversing the wrap point. For example, if
348 the command history were:
349 32766: echo 1
352 32767: echo 2
353 1: echo 3
354 the number -2 refers to command 32767 because it is the second previous
356 command, regardless of serial number.
357
359 None.
360
362 sh
363 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
365 Variables, Section 12.2, Utility Syntax Guidelines
366
368 Portions of this text are reprinted and reproduced in electronic form
369 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
370 table Operating System Interface (POSIX), The Open Group Base Specifi‐
371 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
372 Electrical and Electronics Engineers, Inc and The Open Group. In the
373 event of any discrepancy between this version and the original IEEE and
374 The Open Group Standard, the original IEEE and The Open Group Standard
375 is the referee document. The original Standard can be obtained online
376 at http://www.opengroup.org/unix/online.html .
377 Any typographical or formatting errors that appear in this page are
379 most likely to have been introduced during the conversion of the source
380 files to man page format. To report such errors, see https://www.ker‐
381 nel.org/doc/man-pages/reporting_bugs.html .
382IEEE/The Open Group 2017 FC(1P)