1$OpenBSD: POSIX,v 1.3 1999/06/06 07:03:01 pjanzen 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 expect 19 space or newline can 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) If crypt(3) is available, files can be read and written using DES 32 encryption. The `x' command prompts the user to enter a key used for 33 encrypting/ decrypting subsequent reads and writes. If only a newline 34 is entered as the key, then encryption is disabled. Otherwise, a key 35 is read in the same manner as a password entry. The key remains in 36 effect until encryption is disabled. For more information on the 37 encryption algorithm, see the bdes(1) man page. Encryption/decryption 38 should be fully compatible with SunOS des(1). 39 403) The POSIX interactive global commands `G' and `V' are extended to 41 support multiple commands, including `a', `i' and `c'. The command 42 format is the same as for the global commands `g' and `v', i.e., one 43 command per line with each line, except for the last, ending in a 44 backslash (\). 45 464) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is 47 that <file> arguments are processed for backslash escapes, i.e., any 48 character preceded by a backslash is interpreted literally. If the 49 first unescaped character of a <file> argument is a bang (!), then the 50 rest of the line is interpreted as a shell command, and no escape 51 processing is performed by ed. 52 535) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked 54 as red. This limits editing of files in the local directory only and 55 prohibits shell commands. 56 57DEVIATIONS 58---------- 591) Though ed is not a stream editor, it can be used to edit binary files. 60 To assist in binary editing, when a file containing at least one ASCII 61 NUL character is written, a newline is not appended if it did not 62 already contain one upon reading. In particular, reading /dev/null 63 prior to writing prevents appending a newline to a binary file. 64 65 For example, to create a file with ed containing a single NUL character: 66 $ ed file 67 a 68 ^@ 69 . 70 r /dev/null 71 wq 72 73 Similarly, to remove a newline from the end of binary `file': 74 $ ed file 75 r /dev/null 76 wq 77 782) Since the behavior of `u' (undo) within a `g' (global) command list is 79 not specified by POSIX, it follows the behavior of the SunOS ed: 80 undo forces a global command list to be executed only once, rather than 81 for each line matching a global pattern. In addtion, each instance of 82 `u' within a global command undoes all previous commands (including 83 undo's) in the command list. This seems the best way, since the 84 alternatives are either too complicated to implement or too confusing 85 to use. 86 87 The global/undo combination is useful for masking errors that 88 would otherwise cause a script to fail. For instance, an ed script 89 to remove any occurrences of either `censor1' or `censor2' might be 90 written as: 91 ed - file <<EOF 92 1g/.*/u\ 93 ,s/censor1//g\ 94 ,s/censor2//g 95 ... 96 973) The `m' (move) command within a `g' command list also follows the SunOS 98 ed implementation: any moved lines are removed from the global command's 99 `active' list. 100 1014) If ed is invoked with a name argument prefixed by a bang (!), then the 102 remainder of the argument is interpreted as a shell command. To invoke 103 ed on a file whose name starts with bang, prefix the name with a 104 backslash. 105