1$FreeBSD: src/bin/ed/POSIX,v 1.7.2.1 2000/07/17 10:42:48 sheldonh Exp $ 2$DragonFly: src/bin/ed/POSIX,v 1.2 2003/06/17 04:22:49 dillon 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) 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. 103