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
13 fc — process the command history list
14
16 fc [−r] [−e editor] [first [last]]
17 fc −l [−nr] [first [last]]
19 fc −s [old=new] [first]
21
23 The fc utility shall list, or shall edit and re-execute, commands pre‐
24 viously entered to an interactive sh.
25 The command history list shall reference commands by number. The first
27 number in the list is selected arbitrarily. The relationship of a num‐
28 ber to its command shall not change except when the user logs in and no
29 other process is accessing the list, at which time the system may reset
30 the numbering to start the oldest retained command at another number
31 (usually 1). When the number reaches an implementation-defined upper
32 limit, which shall be no smaller than the value in HISTSIZE or 32767
33 (whichever is greater), the shell may wrap the numbers, starting the
34 next command with a lower number (usually 1). However, despite this
35 optional wrapping of numbers, fc shall maintain the time-ordering
36 sequence of the commands. For example, if four commands in sequence are
37 given the numbers 32766, 32767, 1 (wrapped), and 2 as they are exe‐
38 cuted, command 32767 is considered the command previous to 1, even
39 though its number is higher.
40 When commands are edited (when the −l option is not specified), the
42 resulting lines shall be entered at the end of the history list and
43 then re-executed by sh. The fc command that caused the editing shall
44 not be entered into the history list. If the editor returns a non-zero
45 exit status, this shall suppress the entry into the history list and
46 the command re-execution. Any command line variable assignments or re‐
47 direction operators used with fc shall affect both the fc command
48 itself as well as the command that results; for example:
49 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.1‐2008, 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.1‐2008,
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
130 fc 20 10 fc −r 40 30
131 * When a range of commands is used, it shall not be an
133 error to specify first or last values that are not in the
134 history list; fc shall substitute the value representing
135 the oldest or newest command in the list, as appropriate.
136 For example, if there are only ten commands in the his‐
137 tory list, numbered 1 to 10:
138 fc −l
140 fc 1 99
141 shall list and edit, respectively, all ten commands.
143 old=new Replace the first occurrence of string old in the commands to
145 be re-executed by the string new.
146
148 Not used.
149
151 None.
152
154 The following environment variables shall affect the execution of fc:
155 FCEDIT This variable, when expanded by the shell, shall determine
157 the default value for the −e editor option's editor option-
158 argument. If FCEDIT is null or unset, ed shall be used as the
159 editor.
160 HISTFILE Determine a pathname naming a command history file. If the
162 HISTFILE variable is not set, the shell may attempt to access
163 or create a file .sh_history in the directory referred to by
164 the HOME environment variable. If the shell cannot obtain
165 both read and write access to, or create, the history file,
166 it shall use an unspecified mechanism that allows the history
167 to operate properly. (References to history ``file'' in this
168 section shall be understood to mean this unspecified mecha‐
169 nism in such cases.) An implementation may choose to access
170 this variable only when initializing the history file; this
171 initialization shall occur when fc or sh first attempt to
172 retrieve entries from, or add entries to, the file, as the
173 result of commands issued by the user, the file named by the
174 ENV variable, or implementation-defined system start-up
175 files. In some historical shells, the history file is ini‐
176 tialized just after the ENV file has been processed. There‐
177 fore, it is implementation-defined whether changes made to
178 HISTFILE after the history file has been initialized are
179 effective. Implementations may choose to disable the history
180 list mechanism for users with appropriate privileges who do
181 not set HISTFILE; the specific circumstances under which this
182 occurs are implementation-defined. If more than one instance
183 of the shell is using the same history file, it is unspeci‐
184 fied how updates to the history file from those shells inter‐
185 act. As entries are deleted from the history file, they shall
186 be deleted oldest first. It is unspecified when history file
187 entries are physically removed from the history file.
188 HISTSIZE Determine a decimal number representing the limit to the num‐
190 ber of previous commands that are accessible. If this vari‐
191 able is unset, an unspecified default greater than or equal
192 to 128 shall be used. The maximum number of commands in the
193 history list is unspecified, but shall be at least 128. An
194 implementation may choose to access this variable only when
195 initializing the history file, as described under HISTFILE.
196 Therefore, it is unspecified whether changes made to HISTSIZE
197 after the history file has been initialized are effective.
198 LANG Provide a default value for the internationalization vari‐
200 ables that are unset or null. (See the Base Definitions vol‐
201 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
202 ables for the precedence of internationalization variables
203 used to determine the values of locale categories.)
204 LC_ALL If set to a non-empty string value, override the values of
206 all the other internationalization variables.
207 LC_CTYPE Determine the locale for the interpretation of sequences of
209 bytes of text data as characters (for example, single-byte as
210 opposed to multi-byte characters in arguments and input
211 files).
212 LC_MESSAGES
214 Determine the locale that should be used to affect the format
215 and contents of diagnostic messages written to standard
216 error.
217 NLSPATH Determine the location of message catalogs for the processing
219 of LC_MESSAGES.
220
222 Default.
223
225 When the −l option is used to list commands, the format of each command
226 in the list shall be as follows:
227 "%d\t%s\n", <line number>, <command>
229 If both the −l and −n options are specified, the format of each command
231 shall be:
232 "\t%s\n", <command>
234 If the <command> consists of more than one line, the lines after the
236 first shall be displayed as:
237 "\t%s\n", <continued-command>
239
241 The standard error shall be used only for diagnostic messages.
242
244 None.
245
247 None.
248
250 The following exit values shall be returned:
251 0 Successful completion of the listing.
253 >0 An error occurred.
255 Otherwise, the exit status shall be that of the commands executed by
257 fc.
258
260 Default.
261 The following sections are informative.
263
265 Since editors sometimes use file descriptors as integral parts of their
266 editing, redirecting their file descriptors as part of the fc command
267 can produce unexpected results. For example, if vi is the FCEDIT edi‐
268 tor, the command:
269 fc −s | more
271 does not work correctly on many systems.
273 Users on windowing systems may want to have separate history files for
275 each window by setting HISTFILE as follows:
276 HISTFILE=$HOME/.sh_hist$$
278
280 None.
281
283 This utility is based on the fc built-in of the KornShell.
284 An early proposal specified the −e option as [−e editor [old= new ]],
286 which is not historical practice. Historical practice in fc of either
287 [−e editor] or [−e − [ old= new ]] is acceptable, but not both
288 together. To clarify this, a new option −s was introduced replacing the
289 [−e −]. This resolves the conflict and makes fc conform to the Utility
290 Syntax Guidelines.
291 HISTFILE Some implementations of the KornShell check for the superuser
293 and do not create a history file unless HISTFILE is set. This
294 is done primarily to avoid creating unlinked files in the
295 root file system when logging in during single-user mode.
296 HISTFILE must be set for the superuser to have history.
297 HISTSIZE Needed to limit the size of history files. It is the intent
299 of the standard developers that when two shells share the
300 same history file, commands that are entered in one shell
301 shall be accessible by the other shell. Because of the diffi‐
302 culties of synchronization over a network, the exact nature
303 of the interaction is unspecified.
304 The initialization process for the history file can be dependent on the
306 system start-up files, in that they may contain commands that effec‐
307 tively preempt the settings the user has for HISTFILE and HISTSIZE.
308 For example, function definition commands are recorded in the history
309 file. If the system administrator includes function definitions in some
310 system start-up file called before the ENV file, the history file is
311 initialized before the user can influence its characteristics. In some
312 historical shells, the history file is initialized just after the ENV
313 file has been processed. Because of these situations, the text requires
314 the initialization process to be implementation-defined.
315 Consideration was given to omitting the fc utility in favor of the com‐
317 mand line editing feature in sh. For example, in vi editing mode, typ‐
318 ing "<ESC>v" is equivalent to:
319 EDITOR=vi fc
321 However, the fc utility allows the user the flexibility to edit multi‐
323 ple commands simultaneously (such as fc 10 20) and to use editors other
324 than those supported by sh for command line editing.
325 In the KornShell, the alias r (``re-do'') is preset to fc −e − (equiva‐
327 lent to the POSIX fc −s). This is probably an easier command name to
328 remember than fc (``fix command''), but it does not meet the Utility
329 Syntax Guidelines. Renaming fc to hist or redo was considered, but
330 since this description closely matches historical KornShell practice
331 already, such a renaming was seen as gratuitous. Users are free to
332 create aliases whenever odd historical names such as fc, awk, cat,
333 grep, or yacc are standardized by POSIX.
334 Command numbers have no ordering effects; they are like serial numbers.
336 The −r option and −number operand address the sequence of command exe‐
337 cution, regardless of serial numbers. So, for example, if the command
338 number wrapped back to 1 at some arbitrary point, there would be no
339 ambiguity associated with traversing the wrap point. For example, if
340 the command history were:
341 32766: echo 1
343 32767: echo 2
344 1: echo 3
345 the number −2 refers to command 32767 because it is the second previous
347 command, regardless of serial number.
348
350 None.
351
353 sh
354 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
356 Variables, Section 12.2, Utility Syntax Guidelines
357
359 Portions of this text are reprinted and reproduced in electronic form
360 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
361 -- Portable Operating System Interface (POSIX), The Open Group Base
362 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
363 cal and Electronics Engineers, Inc and The Open Group. (This is
364 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
365 event of any discrepancy between this version and the original IEEE and
366 The Open Group Standard, the original IEEE and The Open Group Standard
367 is the referee document. The original Standard can be obtained online
368 at http://www.unix.org/online.html .
369 Any typographical or formatting errors that appear in this page are
371 most likely to have been introduced during the conversion of the source
372 files to man page format. To report such errors, see https://www.ker‐
373 nel.org/doc/man-pages/reporting_bugs.html .
374IEEE/The Open Group 2013 FC(1P)