2 This version of ed(1) is not strictly POSIX compliant, as described in
3 the POSIX 1003.2 document. The following is a summary of the omissions,
4 extensions and possible deviations from POSIX 1003.2.
8 1) For backwards compatibility, the POSIX rule that says a range of
9 addresses cannot be used where only a single address is expected has
12 2) To support the BSD `s' command (see extension [1] below),
13 substitution patterns cannot be delimited by numbers or the characters
14 `r', `g' and `p'. In contrast, POSIX specifies any character expect
15 space or newline can used as a delimiter.
19 1) BSD commands have been implemented wherever they do not conflict with
20 the POSIX standard. The BSD-ism's included are:
21 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution,
22 ii) `W' for appending text to an existing file,
23 iii) `wq' for exiting after a write,
24 iv) `z' for scrolling through the buffer, and
25 v) BSD line addressing syntax (i.e., `^' and `%') is recognized.
27 2) The POSIX interactive global commands `G' and `V' are extended to
28 support multiple commands, including `a', `i' and `c'. The command
29 format is the same as for the global commands `g' and `v', i.e., one
30 command per line with each line, except for the last, ending in a
33 3) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is
34 that <file> arguments are processed for backslash escapes, i.e., any
35 character preceded by a backslash is interpreted literally. If the
36 first unescaped character of a <file> argument is a bang (!), then the
37 rest of the line is interpreted as a shell command, and no escape
38 processing is performed by ed.
40 4) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked
41 as red. This limits editing of files in the local directory only and
42 prohibits shell commands.
46 1) 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.
52 For example, to create a file with ed containing a single NUL character:
60 Similarly, to remove a newline from the end of binary `file':
65 2) 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
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
84 3) 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
88 4) 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