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jcs's openbsd hax
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1$OpenBSD: POSIX,v 1.8 2014/05/24 01:35:55 daniel Exp $
2$NetBSD: POSIX,v 1.9 1995/03/21 09:04:32 cgd Exp $
3
4This version of ed(1) is not strictly POSIX compliant, as described in
5the POSIX 1003.2 document. The following is a summary of the omissions,
6extensions and possible deviations from POSIX 1003.2.
7
8OMISSIONS
9---------
101) Locale(3) is not supported yet.
11
122) For backwards compatibility, the POSIX rule that says a range of
13 addresses cannot be used where only a single address is expected has
14 been relaxed.
15
163) To support the BSD `s' command (see extension [1] below),
17 substitution patterns cannot be delimited by numbers or the characters
18 `r', `g' and `p'. In contrast, POSIX specifies any character except
19 space or newline can be used as a delimiter.
20
21EXTENSIONS
22----------
231) BSD commands have been implemented wherever they do not conflict with
24 the POSIX standard. The BSD-ism's included are:
25 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution,
26 ii) `W' for appending text to an existing file,
27 iii) `wq' for exiting after a write,
28 iv) `z' for scrolling through the buffer, and
29 v) BSD line addressing syntax (i.e., `^' and `%') is recognized.
30
312) The POSIX interactive global commands `G' and `V' are extended to
32 support multiple commands, including `a', `i' and `c'. The command
33 format is the same as for the global commands `g' and `v', i.e., one
34 command per line with each line, except for the last, ending in a
35 backslash (\).
36
373) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is
38 that <file> arguments are processed for backslash escapes, i.e., any
39 character preceded by a backslash is interpreted literally. If the
40 first unescaped character of a <file> argument is a bang (!), then the
41 rest of the line is interpreted as a shell command, and no escape
42 processing is performed by ed.
43
44DEVIATIONS
45----------
461) Though ed is not a stream editor, it can be used to edit binary files.
47 To assist in binary editing, when a file containing at least one ASCII
48 NUL character is written, a newline is not appended if it did not
49 already contain one upon reading. In particular, reading /dev/null
50 prior to writing prevents appending a newline to a binary file.
51
52 For example, to create a file with ed containing a single NUL character:
53 $ ed file
54 a
55 ^@
56 .
57 r /dev/null
58 wq
59
60 Similarly, to remove a newline from the end of binary `file':
61 $ ed file
62 r /dev/null
63 wq
64
652) Since the behavior of `u' (undo) within a `g' (global) command list is
66 not specified by POSIX, it follows the behavior of the SunOS ed:
67 undo forces a global command list to be executed only once, rather than
68 for each line matching a global pattern. In addition, each instance of
69 `u' within a global command undoes all previous commands (including
70 undo's) in the command list. This seems the best way, since the
71 alternatives are either too complicated to implement or too confusing
72 to use.
73
74 The global/undo combination is useful for masking errors that
75 would otherwise cause a script to fail. For instance, an ed script
76 to remove any occurrences of either `censor1' or `censor2' might be
77 written as:
78 ed - file <<EOF
79 1g/.*/u\
80 ,s/censor1//g\
81 ,s/censor2//g
82 ...
83
843) The `m' (move) command within a `g' command list also follows the SunOS
85 ed implementation: any moved lines are removed from the global command's
86 `active' list.
87
884) If ed is invoked with a name argument prefixed by a bang (!), then the
89 remainder of the argument is interpreted as a shell command. To invoke
90 ed on a file whose name starts with bang, prefix the name with a
91 backslash.