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. 92