1$Id$ 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) Locale(3) is not supported yet. 10 112) For backwards compatibility, the POSIX rule that says a range of 12 addresses cannot be used where only a single address is expected has 13 been relaxed. 14 153) To support the BSD `s' command (see extension [1] below), 16 substitution patterns cannot be delimited by numbers or the characters 17 `r', `g' and `p'. In contrast, POSIX specifies any character expect 18 space or newline can used as a delimiter. 19 20EXTENSIONS 21---------- 221) BSD commands have been implemented wherever they do not conflict with 23 the POSIX standard. The BSD-ism's included are: 24 i) `s' (i.e., s[n][rgp]*) to repeat a previous substitution, 25 ii) `W' for appending text to an existing file, 26 iii) `wq' for exiting after a write, 27 iv) `z' for scrolling through the buffer, and 28 v) BSD line addressing syntax (i.e., `^' and `%') is recognized. 29 302) If crypt(3) is available, files can be read and written using DES 31 encryption. The `x' command prompts the user to enter a key used for 32 encrypting/ decrypting subsequent reads and writes. If only a newline 33 is entered as the key, then encryption is disabled. Otherwise, a key 34 is read in the same manner as a password entry. The key remains in 35 effect until encryption is disabled. For more information on the 36 encryption algorithm, see the bdes(1) man page. Encryption/decryption 37 should be fully compatible with SunOS des(1). 38 393) The POSIX interactive global commands `G' and `V' are extended to 40 support multiple commands, including `a', `i' and `c'. The command 41 format is the same as for the global commands `g' and `v', i.e., one 42 command per line with each line, except for the last, ending in a 43 backslash (\). 44 454) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is 46 that <file> arguments are processed for backslash escapes, i.e., any 47 character preceded by a backslash is interpreted literally. If the 48 first unescaped character of a <file> argument is a bang (!), then the 49 rest of the line is interpreted as a shell command, and no escape 50 processing is performed by ed. 51 525) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked 53 as red. This limits editing of files in the local directory only and 54 prohibits shell commands. 55 56DEVIATIONS 57---------- 581) Though ed is not a stream editor, it can be used to edit binary files. 59 To assist in binary editing, when a file containing at least one ASCII 60 NUL character is written, a newline is not appended if it did not 61 already contain one upon reading. In particular, reading /dev/null 62 prior to writing prevents appending a newline to a binary file. 63 64 For example, to create a file with ed containing a single NUL character: 65 $ ed file 66 a 67 ^@ 68 . 69 r /dev/null 70 wq 71 72 Similarly, to remove a newline from the end of binary `file': 73 $ ed file 74 r /dev/null 75 wq 76 772) Since the behavior of `u' (undo) within a `g' (global) command list is 78 not specified by POSIX, it follows the behavior of the SunOS ed: 79 undo forces a global command list to be executed only once, rather than 80 for each line matching a global pattern. In addtion, each instance of 81 `u' within a global command undoes all previous commands (including 82 undo's) in the command list. This seems the best way, since the 83 alternatives are either too complicated to implement or too confusing 84 to use. 85 86 The global/undo combination is useful for masking errors that 87 would otherwise cause a script to fail. For instance, an ed script 88 to remove any occurences of either `censor1' or `censor2' might be 89 written as: 90 ed - file <<EOF 91 1g/.*/u\ 92 ,s/censor1//g\ 93 ,s/censor2//g 94 ... 95 963) The `m' (move) command within a `g' command list also follows the SunOS 97 ed implementation: any moved lines are removed from the global command's 98 `active' list. 99 1004) If ed is invoked with a name argument prefixed by a bang (!), then the 101 remainder of the argument is interpreted as a shell command. To invoke 102 ed on a file whose name starts with bang, prefix the name with a 103 backslash. 104