1FC(P) POSIX Programmer's Manual FC(P)
2
6 fc - process the command history list
7
9 fc [-r][-e editor] [first[last]]
10 fc -l[-nr] [first[last]]
12 fc -s[old=new][first]
14
17 The fc utility shall list, or shall edit and re-execute, commands pre‐
18 viously entered to an interactive sh.
19 The command history list shall reference commands by number. The first
21 number in the list is selected arbitrarily. The relationship of a num‐
22 ber to its command shall not change except when the user logs in and no
23 other process is accessing the list, at which time the system may reset
24 the numbering to start the oldest retained command at another number
25 (usually 1). When the number reaches an implementation-defined upper
26 limit, which shall be no smaller than the value in HISTSIZE or 32767
27 (whichever is greater), the shell may wrap the numbers, starting the
28 next command with a lower number (usually 1). However, despite this
29 optional wrapping of numbers, fc shall maintain the time-ordering
30 sequence of the commands. For example, if four commands in sequence are
31 given the numbers 32766, 32767, 1 (wrapped), and 2 as they are exe‐
32 cuted, command 32767 is considered the command previous to 1, even
33 though its number is higher.
34 When commands are edited (when the -l option is not specified), the
36 resulting lines shall be entered at the end of the history list and
37 then re-executed by sh. The fc command that caused the editing shall
38 not be entered into the history list. If the editor returns a non-zero
39 exit status, this shall suppress the entry into the history list and
40 the command re-execution. Any command line variable assignments or re‐
41 direction operators used with fc shall affect both the fc command
42 itself as well as the command that results; for example:
43 fc -s -- -1 2>/dev/null
46 reinvokes the previous command, suppressing standard error for both fc
48 and the previous command.
49
51 The fc utility shall conform to the Base Definitions volume of
52 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
53 The following options shall be supported:
55 -e editor
57 Use the editor named by editor to edit the commands. The editor
58 string is a utility name, subject to search via the PATH vari‐
59 able (see the Base Definitions volume of IEEE Std 1003.1-2001,
60 Chapter 8, Environment Variables). The value in the FCEDIT vari‐
61 able shall be used as a default when -e is not specified. If
62 FCEDIT is null or unset, ed shall be used as the editor.
63 -l (The letter ell.) List the commands rather than invoking an edi‐
65 tor on them. The commands shall be written in the sequence indi‐
66 cated by the first and last operands, as affected by -r, with
67 each command preceded by the command number.
68 -n Suppress command numbers when listing with -l.
70 -r Reverse the order of the commands listed (with -l) or edited
72 (with neither -l nor -s).
73 -s Re-execute the command without invoking an editor.
75
78 The following operands shall be supported:
79 first, last
81 Select the commands to list or edit. The number of previous com‐
82 mands that can be accessed shall be determined by the value of
83 the HISTSIZE variable. The value of first or last or both shall
84 be one of the following:
85 [+]number
87 A positive number representing a command number; command numbers
88 can be displayed with the -l option.
89 -number
91 A negative decimal number representing the command that was exe‐
92 cuted number of commands previously. For example, -1 is the
93 immediately previous command.
94 string
96 A string indicating the most recently entered command that
97 begins with that string. If the old= new operand is not also
98 specified with -s, the string form of the first operand cannot
99 contain an embedded equal sign.
100 When the synopsis form with -s is used:
103 * If first is omitted, the previous command shall be used.
105 For the synopsis forms without -s:
107 * If last is omitted, last shall default to the previous com‐
109 mand when -l is specified; otherwise, it shall default to
110 first.
111 * If first and last are both omitted, the previous 16 commands
113 shall be listed or the previous single command shall be
114 edited (based on the -l option).
115 * If first and last are both present, all of the commands from
117 first to last shall be edited (without -l) or listed (with
118 -l). Editing multiple commands shall be accomplished by pre‐
119 senting to the editor all of the commands at one time, each
120 command starting on a new line. If first represents a newer
121 command than last, the commands shall be listed or edited in
122 reverse sequence, equivalent to using -r. For example, the
123 following commands on the first line are equivalent to the
124 corresponding commands on the second:
125 fc -r 10 20 fc 30 40
128 fc 20 10 fc -r 40 30
129 * When a range of commands is used, it shall not be an error to
131 specify first or last values that are not in the history
132 list; fc shall substitute the value representing the oldest
133 or newest command in the list, as appropriate. For example,
134 if there are only ten commands in the history list, numbered
135 1 to 10:
136 fc -l
139 fc 1 99
140 shall list and edit, respectively, all ten commands.
142 old=new
144 Replace the first occurrence of string old in the commands to be
145 re-executed by the string new.
146
149 Not used.
150
152 None.
153
155 The following environment variables shall affect the execution of fc:
156 FCEDIT This variable, when expanded by the shell, shall determine the
158 default value for the -e editor option's editor option-argument.
159 If FCEDIT is null or unset, ed shall be used as the editor.
160 HISTFILE
162 Determine a pathname naming a command history file. If the HIST‐
163 FILE variable is not set, the shell may attempt to access or
164 create a file .sh_history in the directory referred to by the
165 HOME environment variable. If the shell cannot obtain both read
166 and write access to, or create, the history file, it shall use
167 an unspecified mechanism that allows the history to operate
168 properly. (References to history "file" in this section shall be
169 understood to mean this unspecified mechanism in such cases.) An
170 implementation may choose to access this variable only when ini‐
171 tializing the history file; this initialization shall occur when
172 fc or sh first attempt to retrieve entries from, or add entries
173 to, the file, as the result of commands issued by the user, the
174 file named by the ENV variable, or implementation-defined system
175 start-up files. In some historical shells, the history file is
176 initialized just after the ENV file has been processed. There‐
177 fore, it is implementation-defined whether changes made to HIST‐
178 FILE after the history file has been initialized are effective.
179 Implementations may choose to disable the history list mechanism
180 for users with appropriate privileges who do not set HISTFILE ;
181 the specific circumstances under which this occurs are implemen‐
182 tation-defined. If more than one instance of the shell is using
183 the same history file, it is unspecified how updates to the his‐
184 tory file from those shells interact. As entries are deleted
185 from the history file, they shall be deleted oldest first. It
186 is unspecified when history file entries are physically removed
187 from the history file.
188 HISTSIZE
190 Determine a decimal number representing the limit to the number
191 of previous commands that are accessible. If this variable is
192 unset, an unspecified default greater than or equal to 128 shall
193 be used. The maximum number of commands in the history list is
194 unspecified, but shall be at least 128. An implementation may
195 choose to access this variable only when initializing the his‐
196 tory file, as described under HISTFILE . Therefore, it is
197 unspecified whether changes made to HISTSIZE after the history
198 file has been initialized are effective.
199 LANG Provide a default value for the internationalization variables
201 that are unset or null. (See the Base Definitions volume of
202 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
203 ables for the precedence of internationalization variables used
204 to determine the values of locale categories.)
205 LC_ALL If set to a non-empty string value, override the values of all
207 the other internationalization variables.
208 LC_CTYPE
210 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 files).
213 LC_MESSAGES
215 Determine the locale that should be used to affect the format
216 and contents of diagnostic messages written to standard error.
217 NLSPATH
219 Determine the location of message catalogs for the processing of
220 LC_MESSAGES .
221
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
263 fc.
264
266 Default.
267 The following sections are informative.
269
271 Since editors sometimes use file descriptors as integral parts of their
272 editing, redirecting their file descriptors as part of the fc command
273 can produce unexpected results. For example, if vi is the FCEDIT edi‐
274 tor, the command:
275 fc -s | more
278 does not work correctly on many systems.
280 Users on windowing systems may want to have separate history files for
282 each window by setting HISTFILE as follows:
283 HISTFILE=$HOME/.sh_hist$$
286
288 None.
289
291 This utility is based on the fc built-in of the KornShell.
292 An early proposal specified the -e option as [-e editor [ old = new ]],
294 which is not historical practice. Historical practice in fc of either
295 [-e editor ] or [-e - [ old = new ]] is acceptable, but not both
296 together. To clarify this, a new option -s was introduced replacing
297 the [-e -]. This resolves the conflict and makes fc conform to the
298 Utility Syntax Guidelines.
299 HISTFILE
301 Some implementations of the KornShell check for the superuser
302 and do not create a history file unless HISTFILE is set. This
303 is done primarily to avoid creating unlinked files in the root
304 file system when logging in during single-user mode. HISTFILE
305 must be set for the superuser to have history.
306 HISTSIZE
308 Needed to limit the size of history files. It is the intent of
309 the standard developers that when two shells share the same his‐
310 tory file, commands that are entered in one shell shall be
311 accessible by the other shell. Because of the difficulties of
312 synchronization over a network, the exact nature of the interac‐
313 tion is unspecified.
314 The initialization process for the history file can be dependent on the
317 system start-up files, in that they may contain commands that effec‐
318 tively preempt the settings the user has for HISTFILE and HISTSIZE .
319 For example, function definition commands are recorded in the history
320 file. If the system administrator includes function definitions in some
321 system start-up file called before the ENV file, the history file is
322 initialized before the user can influence its characteristics. In some
323 historical shells, the history file is initialized just after the ENV
324 file has been processed. Because of these situations, the text requires
325 the initialization process to be implementation-defined.
326 Consideration was given to omitting the fc utility in favor of the com‐
328 mand line editing feature in sh. For example, in vi editing mode, typ‐
329 ing "<ESC> v" is equivalent to:
330 EDITOR=vi fc
333 However, the fc utility allows the user the flexibility to edit multi‐
335 ple commands simultaneously (such as fc 10 20) and to use editors other
336 than those supported by sh for command line editing.
337 In the KornShell, the alias r (``re-do") is preset to fc -e - (equiva‐
339 lent to the POSIX fc -s). This is probably an easier command name to
340 remember than fc (``fix command"), but it does not meet the Utility
341 Syntax Guidelines. Renaming fc to hist or redo was considered, but
342 since this description closely matches historical KornShell practice
343 already, such a renaming was seen as gratuitous. Users are free to cre‐
344 ate aliases whenever odd historical names such as fc, awk, cat, grep,
345 or yacc are standardized by POSIX.
346 Command numbers have no ordering effects; they are like serial numbers.
348 The -r option and -number operand address the sequence of command exe‐
349 cution, regardless of serial numbers. So, for example, if the command
350 number wrapped back to 1 at some arbitrary point, there would be no
351 ambiguity associated with traversing the wrap point. For example, if
352 the command history were:
353 32766: echo 1
356 32767: echo 2
357 1: echo 3
358 the number -2 refers to command 32767 because it is the second previous
360 command, regardless of serial number.
361
363 None.
364
366 sh
367
369 Portions of this text are reprinted and reproduced in electronic form
370 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
371 -- Portable Operating System Interface (POSIX), The Open Group Base
372 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
373 Electrical and Electronics Engineers, Inc and The Open Group. In the
374 event of any discrepancy between this version and the original IEEE and
375 The Open Group Standard, the original IEEE and The Open Group Standard
376 is the referee document. The original Standard can be obtained online
377 at http://www.opengroup.org/unix/online.html .
378IEEE/The Open Group 2003 FC(P)