1 2This version of ed(1) is not strictly POSIX compliant, as described in 3the POSIX 1003.2 document. The following is a summary of the omissions, 4extensions and possible deviations from POSIX 1003.2. 5 6OMISSIONS 7--------- 81) For backwards compatibility, the POSIX rule that says a range of 9 addresses cannot be used where only a single address is expected has 10 been relaxed. 11 122) 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. 16 17EXTENSIONS 18---------- 191) 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. 26 272) 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 31 backslash (\). 32 333) 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. 39 404) 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. 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