summaryrefslogtreecommitdiffstats
path: root/bin/ed/ed.1
blob: 9e68a6e3e66c1d7536fd6951e9ef6c90beec460b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
.\" $FreeBSD$
.Dd May 21, 1993
.Dt ED 1
.Os
.Sh NAME
.Nm ed ,
.Nm red
.Nd text editor
.Sh SYNOPSIS
.Nm
.Op Fl
.Op Fl sx
.Op Fl p Ar string
.Op Ar file
.Nm red
.Op Fl
.Op Fl sx
.Op Fl p Ar string
.Op Ar file
.Sh DESCRIPTION
The
.Nm
utility is a line-oriented text editor.
It is used to create, display, modify and otherwise manipulate text
files.
When invoked as
.Nm red ,
the editor runs in
.Qq restricted
mode, in which the only difference is that the editor restricts the
use of filenames which start with
.Ql \&!
(interpreted as shell commands by
.Nm )
or contain a
.Ql \&/ .
Note that editing outside of the current directory is only prohibited
if the user does not have write access to the current directory.
If a user has write access to the current directory, then symbolic
links can be created in the current directory, in which case
.Nm red
will not stop the user from editing the file that the symbolic link
points to.
.Pp
If invoked with a
.Ar file
argument, then a copy of
.Ar file
is read into the editor's buffer.
Changes are made to this copy and not directly to
.Ar file
itself.
Upon quitting
.Nm ,
any changes not explicitly saved with a
.Em w
command are lost.
.Pp
Editing is done in two distinct modes:
.Em command
and
.Em input .
When first invoked,
.Nm
is in command mode.
In this mode commands are read from the standard input and
executed to manipulate the contents of the editor buffer.
A typical command might look like:
.Pp
.Sm off
.Cm ,s No / Em old Xo
.No / Em new
.No / Cm g
.Xc
.Sm on
.Pp
which replaces all occurrences of the string
.Em old
with
.Em new .
.Pp
When an input command, such as
.Em a
(append),
.Em i
(insert) or
.Em c
(change), is given,
.Nm
enters input mode.
This is the primary means
of adding text to a file.
In this mode, no commands are available;
instead, the standard input is written
directly to the editor buffer.
Lines consist of text up to and
including a
.Em newline
character.
Input mode is terminated by
entering a single period
.Pq Em .\&
on a line.
.Pp
All
.Nm
commands operate on whole lines or ranges of lines; e.g.,
the
.Em d
command deletes lines; the
.Em m
command moves lines, and so on.
It is possible to modify only a portion of a line by means of replacement,
as in the example above.
However even here, the
.Em s
command is applied to whole lines at a time.
.Pp
In general,
.Nm
commands consist of zero or more line addresses, followed by a single
character command and possibly additional parameters; i.e.,
commands have the structure:
.Pp
.Sm off
.Xo
.Op Ar address Op , Ar address
.Ar command Op Ar parameters
.Xc
.Sm on
.Pp
The address(es) indicate the line or range of lines to be affected by the
command.
If fewer addresses are given than the command accepts, then
default addresses are supplied.
.Sh OPTIONS
The following options are available:
.Bl -tag -width indent
.It Fl s
Suppress diagnostics.
This should be used if
.Nm Ns 's
standard input is from a script.
.It Fl x
Prompt for an encryption key to be used in subsequent reads and writes
(see the
.Em x
command).
.It Fl p Ar string
Specify a command prompt.
This may be toggled on and off with the
.Em P
command.
.It Ar file
Specify the name of a file to read.
If
.Ar file
is prefixed with a
bang (!), then it is interpreted as a shell command.
In this case,
what is read is
the standard output of
.Ar file
executed via
.Xr sh 1 .
To read a file whose name begins with a bang, prefix the
name with a backslash (\\).
The default filename is set to
.Ar file
only if it is not prefixed with a bang.
.El
.Sh LINE ADDRESSING
An address represents the number of a line in the buffer.
The
.Nm
utility maintains a
.Em current address
which is
typically supplied to commands as the default address when none is specified.
When a file is first read, the current address is set to the last line
of the file.
In general, the current address is set to the last line
affected by a command.
.Pp
A line address is
constructed from one of the bases in the list below, optionally followed
by a numeric offset.
The offset may include any combination
of digits, operators (i.e.,
.Em + ,
.Em -
and
.Em ^ )
and whitespace.
Addresses are read from left to right, and their values are computed
relative to the current address.
.Pp
One exception to the rule that addresses represent line numbers is the
address
.Em 0
(zero).
This means "before the first line,"
and is legal wherever it makes sense.
.Pp
An address range is two addresses separated either by a comma or
semi-colon.
The value of the first address in a range cannot exceed the
value of the second.
If only one address is given in a range, then
the second address is set to the given address.
If an
.Em n Ns -tuple
of addresses is given where
.Em "n\ >\ 2" ,
then the corresponding range is determined by the last two addresses in
the
.Em n Ns -tuple .
If only one address is expected, then the last address is used.
.Pp
Each address in a comma-delimited range is interpreted relative to the
current address.
In a semi-colon-delimited range, the first address is
used to set the current address, and the second address is interpreted
relative to the first.
.Pp
The following address symbols are recognized:
.Bl -tag -width indent
.It .
The current line (address) in the buffer.
.It $
The last line in the buffer.
.It n
The
.Em n Ns th,
line in the buffer
where
.Em n
is a number in the range
.Em [0,$] .
.It - or ^
The previous line.
This is equivalent to
.Em -1
and may be repeated with cumulative effect.
.It -n or ^n
The
.Em n Ns th
previous line, where
.Em n
is a non-negative number.
.It +
The next line.
This is equivalent to
.Em +1
and may be repeated with cumulative effect.
.It +n
The
.Em n Ns th
next line, where
.Em n
is a non-negative number.
.It , or %
The first through last lines in the buffer.
This is equivalent to
the address range
.Em 1,$ .
.It ;
The current through last lines in the buffer.
This is equivalent to
the address range
.Em .,$ .
.It /re/
The next line containing the regular expression
.Em re .
The search wraps to the beginning of the buffer and continues down to the
current line, if necessary.
// repeats the last search.
.It ?re?
The
previous line containing the regular expression
.Em re .
The search wraps to the end of the buffer and continues up to the
current line, if necessary.
?? repeats the last search.
.It 'lc
The
line previously marked by a
.Em k
(mark) command, where
.Em lc
is a lower case letter.
.El
.Sh REGULAR EXPRESSIONS
Regular expressions are patterns used in selecting text.
For example, the command:
.Pp
.Sm off
.Cm g No / Em string Xo
.No /
.Xc
.Sm on
.Pp
prints all lines containing
.Em string .
Regular expressions are also
used by the
.Em s
command for selecting old text to be replaced with new.
.Pp
In addition to a specifying string literals, regular expressions can
represent
classes of strings.
Strings thus represented are said to be matched
by the corresponding regular expression.
If it is possible for a regular expression
to match several strings in a line, then the left-most longest match is
the one selected.
.Pp
The following symbols are used in constructing regular expressions:
.Bl -tag -width indent
.It c
Any character
.Em c
not listed below, including
.Ql \&{ ,
.Ql \&} ,
.Ql \&( ,
.Ql \&) ,
.Ql <
and
.Ql > ,
matches itself.
.It Pf \e c
Any backslash-escaped character
.Em c ,
except for
.Ql \&{ ,
.Ql \&} ,
.Ql \&( ,
.Ql \&) ,
.Ql <
and
.Ql > ,
matches itself.
.It .
Match any single character.
.It Op char-class
Match any single character in
.Em char-class .
To include a
.Ql \&]
in
.Em char-class ,
it must be the first character.
A range of characters may be specified by separating the end characters
of the range with a
.Ql - ,
e.g.,
.Ql a-z
specifies the lower case characters.
The following literal expressions can also be used in
.Em char-class
to specify sets of characters:
.Pp
.Bl -column "[:alnum:]" "[:cntrl:]" "[:lower:]" "[:xdigit:]" -compact
.It [:alnum:] Ta [:cntrl:] Ta [:lower:] Ta [:space:]
.It [:alpha:] Ta [:digit:] Ta [:print:] Ta [:upper:]
.It [:blank:] Ta [:graph:] Ta [:punct:] Ta [:xdigit:]
.El
.Pp
If
.Ql -
appears as the first or last
character of
.Em char-class ,
then it matches itself.
All other characters in
.Em char-class
match themselves.
.Pp
Patterns in
.Em char-class
of the form:
.Pp
.Bl -item -compact -offset 2n
.It
.Op \&. Ns Ar col-elm Ns .\&
or,
.It
.Op = Ns Ar col-elm Ns =
.El
.Pp
where
.Ar col-elm
is a
.Em collating element
are interpreted according to the current locale settings
(not currently supported).
See
.Xr regex 3
and
.Xr re_format 7
for an explanation of these constructs.
.It Op ^char-class
Match any single character, other than newline, not in
.Em char-class .
.Em Char-class
is defined
as above.
.It ^
If
.Em ^
is the first character of a regular expression, then it
anchors the regular expression to the beginning of a line.
Otherwise, it matches itself.
.It $
If
.Em $
is the last character of a regular expression, it
anchors the regular expression to the end of a line.
Otherwise, it matches itself.
.It Pf \e <
Anchor the single character regular expression or subexpression
immediately following it to the beginning of a word.
(This may not be available)
.It Pf \e >
Anchor the single character regular expression or subexpression
immediately following it to the end of a word.
(This may not be available)
.It Pf \e (re\e)
Define a subexpression
.Em re .
Subexpressions may be nested.
A subsequent backreference of the form
.Pf \e Em n ,
where
.Em n
is a number in the range [1,9], expands to the text matched by the
.Em n Ns th
subexpression.
For example, the regular expression
.Ql \e(.*\e)\e1
matches any string
consisting of identical adjacent substrings.
Subexpressions are ordered relative to
their left delimiter.
.It *
Match the single character regular expression or subexpression
immediately preceding it zero or more times.
If
.Em *
is the first
character of a regular expression or subexpression, then it matches
itself.
The
.Em *
operator sometimes yields unexpected results.
For example, the regular expression
.Ql b*
matches the beginning of
the string
.Ql abbb
(as opposed to the substring
.Ql bbb ) ,
since a null match
is the only left-most match.
.It \e{n,m\e} or \e{n,\e} or \e{n\e}
Match the single character regular expression or subexpression
immediately preceding it at least
.Em n
and at most
.Em m
times.
If
.Em m
is omitted, then it matches at least
.Em n
times.
If the comma is also omitted, then it matches exactly
.Em n
times.
.El
.Pp
Additional regular expression operators may be defined depending on the
particular
.Xr regex 3
implementation.
.Sh COMMANDS
All
.Nm
commands are single characters, though some require additional parameters.
If a command's parameters extend over several lines, then
each line except for the last
must be terminated with a backslash (\\).
.Pp
In general, at most one command is allowed per line.
However, most commands accept a print suffix, which is any of
.Em p
(print),
.Em l
(list),
or
.Em n
(enumerate),
to print the last line affected by the command.
.Pp
An interrupt (typically ^C) has the effect of aborting the current command
and returning the editor to command mode.
.Pp
The
.Nm
utility
recognizes the following commands.
The commands are shown together with
the default address or address range supplied if none is
specified (in parenthesis).
.Bl -tag -width indent
.It (.)a
Append text to the buffer after the addressed line.
Text is entered in input mode.
The current address is set to last line entered.
.It (.,.)c
Change lines in the buffer.
The addressed lines are deleted
from the buffer, and text is appended in their place.
Text is entered in input mode.
The current address is set to last line entered.
.It (.,.)d
Delete the addressed lines from the buffer.
If there is a line after the deleted range, then the current address is set
to this line.
Otherwise the current address is set to the line
before the deleted range.
.It e Ar file
Edit
.Ar file ,
and sets the default filename.
If
.Ar file
is not specified, then the default filename is used.
Any lines in the buffer are deleted before
the new file is read.
The current address is set to the last line read.
.It e Ar !command
Edit the standard output of
.Ar !command ,
(see
.Ar !command
below).
The default filename is unchanged.
Any lines in the buffer are deleted before the output of
.Ar command
is read.
The current address is set to the last line read.
.It E Ar file
Edit
.Ar file
unconditionally.
This is similar to the
.Em e
command,
except that unwritten changes are discarded without warning.
The current address is set to the last line read.
.It f Ar file
Set the default filename to
.Ar file .
If
.Ar file
is not specified, then the default unescaped filename is printed.
.It (1,$)g/re/command-list
Apply
.Ar command-list
to each of the addressed lines matching a regular expression
.Ar re .
The current address is set to the
line currently matched before
.Ar command-list
is executed.
At the end of the
.Em g
command, the current address is set to the last line affected by
.Ar command-list .
.Pp
Each command in
.Ar command-list
must be on a separate line,
and every line except for the last must be terminated by a backslash
(\\).
Any commands are allowed, except for
.Em g ,
.Em G ,
.Em v ,
and
.Em V .
A newline alone in
.Ar command-list
is equivalent to a
.Em p
command.
.It (1,$)G/re/
Interactively edit the addressed lines matching a regular expression
.Ar re .
For each matching line,
the line is printed,
the current address is set,
and the user is prompted to enter a
.Ar command-list .
At the end of the
.Em G
command, the current address
is set to the last line affected by (the last)
.Ar command-list .
.Pp
The format of
.Ar command-list
is the same as that of the
.Em g
command.
A newline alone acts as a null command list.
A single
.Ql &
repeats the last non-null command list.
.It H
Toggle the printing of error explanations.
By default, explanations are not printed.
It is recommended that ed scripts begin with this command to
aid in debugging.
.It h
Print an explanation of the last error.
.It (.)i
Insert text in the buffer before the current line.
Text is entered in input mode.
The current address is set to the last line entered.
.It (.,.+1)j
Join the addressed lines.
The addressed lines are
deleted from the buffer and replaced by a single
line containing their joined text.
The current address is set to the resultant line.
.It (.)klc
Mark a line with a lower case letter
.Em lc .
The line can then be addressed as
.Em 'lc
(i.e., a single quote followed by
.Em lc )
in subsequent commands.
The mark is not cleared until the line is
deleted or otherwise modified.
.It (.,.)l
Print the addressed lines unambiguously.
If a single line fills for than one screen (as might be the case
when viewing a binary file, for instance), a
.Dq Li --More--
prompt is printed on the last line.
The
.Nm
utility waits until the RETURN key is pressed
before displaying the next screen.
The current address is set to the last line
printed.
.It (.,.)m(.)
Move lines in the buffer.
The addressed lines are moved to after the
right-hand destination address, which may be the address
.Em 0
(zero).
The current address is set to the
last line moved.
.It (.,.)n
Print the addressed lines along with
their line numbers.
The current address is set to the last line
printed.
.It (.,.)p
Print the addressed lines.
The current address is set to the last line
printed.
.It P
Toggle the command prompt on and off.
Unless a prompt was specified by with command-line option
.Fl p Ar string ,
the command prompt is by default turned off.
.It q
Quit
.Nm .
.It Q
Quit
.Nm
unconditionally.
This is similar to the
.Em q
command,
except that unwritten changes are discarded without warning.
.It ($)r Ar file
Read
.Ar file
to after the addressed line.
If
.Ar file
is not specified, then the default
filename is used.
If there was no default filename prior to the command,
then the default filename is set to
.Ar file .
Otherwise, the default filename is unchanged.
The current address is set to the last line read.
.It ($)r Ar !command
Read
to after the addressed line
the standard output of
.Ar !command ,
(see the
.Ar !command
below).
The default filename is unchanged.
The current address is set to the last line read.
.It (.,.)s/re/replacement/
.It (.,.)s/re/replacement/g
.It (.,.)s/re/replacement/n
Replace text in the addressed lines
matching a regular expression
.Ar re
with
.Ar replacement .
By default, only the first match in each line is replaced.
If the
.Em g
(global) suffix is given, then every match to be replaced.
The
.Em n
suffix, where
.Em n
is a positive number, causes only the
.Em n Ns th
match to be replaced.
It is an error if no substitutions are performed on any of the addressed
lines.
The current address is set the last line affected.
.Pp
.Ar Re
and
.Ar replacement
may be delimited by any character other than space and newline
(see the
.Em s
command below).
If one or two of the last delimiters is omitted, then the last line
affected is printed as though the print suffix
.Em p
were specified.
.Pp
An unescaped
.Ql &
in
.Ar replacement
is replaced by the currently matched text.
The character sequence
.Em \em ,
where
.Em m
is a number in the range [1,9], is replaced by the
.Em m th
backreference expression of the matched text.
If
.Ar replacement
consists of a single
.Ql % ,
then
.Ar replacement
from the last substitution is used.
Newlines may be embedded in
.Ar replacement
if they are escaped with a backslash (\\).
.It (.,.)s
Repeat the last substitution.
This form of the
.Em s
command accepts a count suffix
.Em n ,
or any combination of the characters
.Em r ,
.Em g ,
and
.Em p .
If a count suffix
.Em n
is given, then only the
.Em n Ns th
match is replaced.
The
.Em r
suffix causes
the regular expression of the last search to be used instead of the
that of the last substitution.
The
.Em g
suffix toggles the global suffix of the last substitution.
The
.Em p
suffix toggles the print suffix of the last substitution
The current address is set to the last line affected.
.It (.,.)t(.)
Copy (i.e., transfer) the addressed lines to after the right-hand
destination address, which may be the address
.Em 0
(zero).
The current address is set to the last line
copied.
.It u
Undo the last command and restores the current address
to what it was before the command.
The global commands
.Em g ,
.Em G ,
.Em v ,
and
.Em V .
are treated as a single command by undo.
.Em u
is its own inverse.
.It (1,$)v/re/command-list
Apply
.Ar command-list
to each of the addressed lines not matching a regular expression
.Ar re .
This is similar to the
.Em g
command.
.It (1,$)V/re/
Interactively edit the addressed lines not matching a regular expression
.Ar re .
This is similar to the
.Em G
command.
.It (1,$)w Ar file
Write the addressed lines to
.Ar file .
Any previous contents of
.Ar file
is lost without warning.
If there is no default filename, then the default filename is set to
.Ar file ,
otherwise it is unchanged.
If no filename is specified, then the default
filename is used.
The current address is unchanged.
.It (1,$)wq Ar file
Write the addressed lines to
.Ar file ,
and then executes a
.Em q
command.
.It (1,$)w Ar !command
Write the addressed lines to the standard input of
.Ar !command ,
(see the
.Em !command
below).
The default filename and current address are unchanged.
.It (1,$)W Ar file
Append the addressed lines to the end of
.Ar file .
This is similar to the
.Em w
command, expect that the previous contents of file is not clobbered.
The current address is unchanged.
.It x
Prompt for an encryption key which is used in subsequent reads and
writes.
If a newline alone is entered as the key, then encryption is
turned off.
Otherwise, echoing is disabled while a key is read.
Encryption/decryption is done using the
.Xr bdes 1
algorithm.
.It Pf (.+1)z n
Scroll
.Ar n
lines at a time starting at addressed line.
If
.Ar n
is not specified, then the current window size is used.
The current address is set to the last line printed.
.It !command
Execute
.Ar command
via
.Xr sh 1 .
If the first character of
.Ar command
is
.Ql \&! ,
then it is replaced by text of the
previous
.Ar !command .
The
.Nm
utility does not process
.Ar command
for backslash (\\) escapes.
However, an unescaped
.Em %
is replaced by the default filename.
When the shell returns from execution, a
.Ql \&!
is printed to the standard output.
The current line is unchanged.
.It ($)=
Print the line number of the addressed line.
.It (.+1)newline
Print the addressed line, and sets the current address to
that line.
.El
.Sh FILES
.Bl -tag -width /tmp/ed.* -compact
.It /tmp/ed.*
buffer file
.It ed.hup
the file to which
.Nm
attempts to write the buffer if the terminal hangs up
.El
.Sh SEE ALSO
.Xr bdes 1 ,
.Xr sed 1 ,
.Xr sh 1 ,
.Xr vi 1 ,
.Xr regex 3
.Pp
USD:12-13
.Rs
.%A B. W. Kernighan
.%A P. J. Plauger
.%B Software Tools in Pascal
.%O Addison-Wesley
.%D 1981
.Re
.Sh LIMITATIONS
The
.Nm
utility processes
.Ar file
arguments for backslash escapes, i.e., in a filename,
any characters preceded by a backslash (\\) are
interpreted literally.
.Pp
If a text (non-binary) file is not terminated by a newline character,
then
.Nm
appends one on reading/writing it.
In the case of a binary file,
.Nm
does not append a newline on reading/writing.
.Pp
per line overhead: 4 ints
.Sh DIAGNOSTICS
When an error occurs,
.Nm
prints a
.Ql \&?
and either returns to command mode
or exits if its input is from a script.
An explanation of the last error can be
printed with the
.Em h
(help) command.
.Pp
Since the
.Em g
(global) command masks any errors from failed searches and substitutions,
it can be used to perform conditional operations in scripts; e.g.,
.Pp
.Sm off
.Cm g No / Em old Xo
.No / Cm s
.No // Em new
.No /
.Xc
.Sm on
.Pp
replaces any occurrences of
.Em old
with
.Em new .
If the
.Em u
(undo) command occurs in a global command list, then
the command list is executed only once.
.Pp
If diagnostics are not disabled, attempting to quit
.Nm
or edit another file before writing a modified buffer
results in an error.
If the command is entered a second time, it succeeds,
but any changes to the buffer are lost.
.Sh HISTORY
An
.Nm
command appeared in
Version 1 AT&T UNIX.
OpenPOWER on IntegriCloud