3This version of ed(1) is not strictly POSIX compliant, as described in
4the POSIX 1003.2 document. The following is a summary of the omissions,
5extensions and possible deviations from POSIX 1003.2.
6
7OMISSIONS
8---------
91) Locale(3) is not supported yet.
10
112) For backwards compatibility, the POSIX rule that says a range of
12 addresses cannot be used where only a single address is expected has
13 been relaxed.
14
153) To support the BSD `s' command (see extension [1] below),
16 substitution patterns cannot be delimited by numbers or the characters
17 `r', `g' and `p'. In contrast, POSIX specifies any character expect
18 space or newline can used as a delimiter.
19
20EXTENSIONS
21----------
221) BSD commands have been implemented wherever they do not conflict with
23 the POSIX standard. The BSD-ism's included are:
24 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution,
25 ii) `W' for appending text to an existing file,
26 iii) `wq' for exiting after a write,
27 iv) `z' for scrolling through the buffer, and
28 v) BSD line addressing syntax (i.e., `^' and `%') is recognized.
29
302) If crypt(3) is available, files can be read and written using DES
31 encryption. The `x' command prompts the user to enter a key used for
32 encrypting/ decrypting subsequent reads and writes. If only a newline
33 is entered as the key, then encryption is disabled. Otherwise, a key
34 is read in the same manner as a password entry. The key remains in
35 effect until encryption is disabled. For more information on the
36 encryption algorithm, see the bdes(1) man page. Encryption/decryption
37 should be fully compatible with SunOS des(1).
38
393) The POSIX interactive global commands `G' and `V' are extended to
40 support multiple commands, including `a', `i' and `c'. The command
41 format is the same as for the global commands `g' and `v', i.e., one
42 command per line with each line, except for the last, ending in a
43 backslash (\).
44
454) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is
46 that <file> arguments are processed for backslash escapes, i.e., any
47 character preceded by a backslash is interpreted literally. If the
48 first unescaped character of a <file> argument is a bang (!), then the
49 rest of the line is interpreted as a shell command, and no escape
50 processing is performed by ed.
51
525) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked
53 as red. This limits editing of files in the local directory only and
54 prohibits shell commands.
55
56DEVIATIONS
57----------
581) Though ed is not a stream editor, it can be used to edit binary files.
59 To assist in binary editing, when a file containing at least one ASCII
60 NUL character is written, a newline is not appended if it did not
61 already contain one upon reading. In particular, reading /dev/null
62 prior to writing prevents appending a newline to a binary file.
63
64 For example, to create a file with ed containing a single NUL character:
65 $ ed file
66 a
67 ^@
68 .
69 r /dev/null
70 wq
71
72 Similarly, to remove a newline from the end of binary `file':
73 $ ed file
74 r /dev/null
75 wq
76
772) Since the behavior of `u' (undo) within a `g' (global) command list is
78 not specified by POSIX, it follows the behavior of the SunOS ed:
79 undo forces a global command list to be executed only once, rather than
80 for each line matching a global pattern. In addtion, each instance of
81 `u' within a global command undoes all previous commands (including
82 undo's) in the command list. This seems the best way, since the
83 alternatives are either too complicated to implement or too confusing
84 to use.
85
86 The global/undo combination is useful for masking errors that
87 would otherwise cause a script to fail. For instance, an ed script
88 to remove any occurences of either `censor1' or `censor2' might be
89 written as:
90 ed - file <<EOF
91 1g/.*/u\
92 ,s/censor1//g\
93 ,s/censor2//g
94 ...
95
963) The `m' (move) command within a `g' command list also follows the SunOS
97 ed implementation: any moved lines are removed from the global command's
98 `active' list.
99
1004) If ed is invoked with a name argument prefixed by a bang (!), then the
101 remainder of the argument is interpreted as a shell command. To invoke
102 ed on a file whose name starts with bang, prefix the name with a
103 backslash.
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