Add the DragonFly cvs id and perform general cleanups on cvs/rcs/sccs ids. Most
[dragonfly.git] / bin / ed / POSIX
CommitLineData
984263bc 1$FreeBSD: src/bin/ed/POSIX,v 1.7.2.1 2000/07/17 10:42:48 sheldonh Exp $
1de703da 2$DragonFly: src/bin/ed/POSIX,v 1.2 2003/06/17 04:22:49 dillon Exp $
984263bc
MD
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) For backwards compatibility, the POSIX rule that says a range of
11 addresses cannot be used where only a single address is expected has
12 been relaxed.
13
142) To support the BSD `s' command (see extension [1] below),
15 substitution patterns cannot be delimited by numbers or the characters
16 `r', `g' and `p'. In contrast, POSIX specifies any character expect
17 space or newline can used as a delimiter.
18
19EXTENSIONS
20----------
211) BSD commands have been implemented wherever they do not conflict with
22 the POSIX standard. The BSD-ism's included are:
23 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution,
24 ii) `W' for appending text to an existing file,
25 iii) `wq' for exiting after a write,
26 iv) `z' for scrolling through the buffer, and
27 v) BSD line addressing syntax (i.e., `^' and `%') is recognized.
28
292) If crypt(3) is available, files can be read and written using DES
30 encryption. The `x' command prompts the user to enter a key used for
31 encrypting/ decrypting subsequent reads and writes. If only a newline
32 is entered as the key, then encryption is disabled. Otherwise, a key
33 is read in the same manner as a password entry. The key remains in
34 effect until encryption is disabled. For more information on the
35 encryption algorithm, see the bdes(1) man page. Encryption/decryption
36 should be fully compatible with SunOS des(1).
37
383) The POSIX interactive global commands `G' and `V' are extended to
39 support multiple commands, including `a', `i' and `c'. The command
40 format is the same as for the global commands `g' and `v', i.e., one
41 command per line with each line, except for the last, ending in a
42 backslash (\).
43
444) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is
45 that <file> arguments are processed for backslash escapes, i.e., any
46 character preceded by a backslash is interpreted literally. If the
47 first unescaped character of a <file> argument is a bang (!), then the
48 rest of the line is interpreted as a shell command, and no escape
49 processing is performed by ed.
50
515) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked
52 as red. This limits editing of files in the local directory only and
53 prohibits shell commands.
54
55DEVIATIONS
56----------
571) Though ed is not a stream editor, it can be used to edit binary files.
58 To assist in binary editing, when a file containing at least one ASCII
59 NUL character is written, a newline is not appended if it did not
60 already contain one upon reading. In particular, reading /dev/null
61 prior to writing prevents appending a newline to a binary file.
62
63 For example, to create a file with ed containing a single NUL character:
64 $ ed file
65 a
66 ^@
67 .
68 r /dev/null
69 wq
70
71 Similarly, to remove a newline from the end of binary `file':
72 $ ed file
73 r /dev/null
74 wq
75
762) Since the behavior of `u' (undo) within a `g' (global) command list is
77 not specified by POSIX, it follows the behavior of the SunOS ed:
78 undo forces a global command list to be executed only once, rather than
79 for each line matching a global pattern. In addtion, each instance of
80 `u' within a global command undoes all previous commands (including
81 undo's) in the command list. This seems the best way, since the
82 alternatives are either too complicated to implement or too confusing
83 to use.
84
85 The global/undo combination is useful for masking errors that
86 would otherwise cause a script to fail. For instance, an ed script
87 to remove any occurences of either `censor1' or `censor2' might be
88 written as:
89 ed - file <<EOF
90 1g/.*/u\
91 ,s/censor1//g\
92 ,s/censor2//g
93 ...
94
953) The `m' (move) command within a `g' command list also follows the SunOS
96 ed implementation: any moved lines are removed from the global command's
97 `active' list.
98
994) If ed is invoked with a name argument prefixed by a bang (!), then the
100 remainder of the argument is interpreted as a shell command. To invoke
101 ed on a file whose name starts with bang, prefix the name with a
102 backslash.