1$FreeBSD$ 2 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) For backwards compatibility, the POSIX rule that says a range of 10 addresses cannot be used where only a single address is expected has 11 been relaxed. 12 132) To support the BSD `s' command (see extension [1] below), 14 substitution patterns cannot be delimited by numbers or the characters 15 `r', `g' and `p'. In contrast, POSIX specifies any character expect 16 space or newline can used as a delimiter. 17 18EXTENSIONS 19---------- 201) BSD commands have been implemented wherever they do not conflict with 21 the POSIX standard. The BSD-ism's included are: 22 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution, 23 ii) `W' for appending text to an existing file, 24 iii) `wq' for exiting after a write, 25 iv) `z' for scrolling through the buffer, and 26 v) BSD line addressing syntax (i.e., `^' and `%') is recognized. 27 282) The POSIX interactive global commands `G' and `V' are extended to 29 support multiple commands, including `a', `i' and `c'. The command 30 format is the same as for the global commands `g' and `v', i.e., one 31 command per line with each line, except for the last, ending in a 32 backslash (\). 33 343) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is 35 that <file> arguments are processed for backslash escapes, i.e., any 36 character preceded by a backslash is interpreted literally. If the 37 first unescaped character of a <file> argument is a bang (!), then the 38 rest of the line is interpreted as a shell command, and no escape 39 processing is performed by ed. 40 414) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked 42 as red. This limits editing of files in the local directory only and 43 prohibits shell commands. 44 45DEVIATIONS 46---------- 471) Though ed is not a stream editor, it can be used to edit binary files. 48 To assist in binary editing, when a file containing at least one ASCII 49 NUL character is written, a newline is not appended if it did not 50 already contain one upon reading. In particular, reading /dev/null 51 prior to writing prevents appending a newline to a binary file. 52 53 For example, to create a file with ed containing a single NUL character: 54 $ ed file 55 a 56 ^@ 57 . 58 r /dev/null 59 wq 60 61 Similarly, to remove a newline from the end of binary `file': 62 $ ed file 63 r /dev/null 64 wq 65 662) Since the behavior of `u' (undo) within a `g' (global) command list is 67 not specified by POSIX, it follows the behavior of the SunOS ed: 68 undo forces a global command list to be executed only once, rather than 69 for each line matching a global pattern. In addition, each instance of 70 `u' within a global command undoes all previous commands (including 71 undo's) in the command list. This seems the best way, since the 72 alternatives are either too complicated to implement or too confusing 73 to use. 74 75 The global/undo combination is useful for masking errors that 76 would otherwise cause a script to fail. For instance, an ed script 77 to remove any occurrences of either `censor1' or `censor2' might be 78 written as: 79 ed - file <<EOF 80 1g/.*/u\ 81 ,s/censor1//g\ 82 ,s/censor2//g 83 ... 84 853) The `m' (move) command within a `g' command list also follows the SunOS 86 ed implementation: any moved lines are removed from the global command's 87 `active' list. 88 894) If ed is invoked with a name argument prefixed by a bang (!), then the 90 remainder of the argument is interpreted as a shell command. To invoke 91 ed on a file whose name starts with bang, prefix the name with a 92 backslash. 93