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) If crypt(3) is available, files can be read and written using DES 29 encryption. The `x' command prompts the user to enter a key used for 30 encrypting/ decrypting subsequent reads and writes. If only a newline 31 is entered as the key, then encryption is disabled. Otherwise, a key 32 is read in the same manner as a password entry. The key remains in 33 effect until encryption is disabled. For more information on the 34 encryption algorithm, see the bdes(1) man page. Encryption/decryption 35 should be fully compatible with SunOS des(1). 36 373) The POSIX interactive global commands `G' and `V' are extended to 38 support multiple commands, including `a', `i' and `c'. The command 39 format is the same as for the global commands `g' and `v', i.e., one 40 command per line with each line, except for the last, ending in a 41 backslash (\). 42 434) An extension to the POSIX file commands `E', `e', `r', `W' and `w' is 44 that <file> arguments are processed for backslash escapes, i.e., any 45 character preceded by a backslash is interpreted literally. If the 46 first unescaped character of a <file> argument is a bang (!), then the 47 rest of the line is interpreted as a shell command, and no escape 48 processing is performed by ed. 49 505) For SunOS ed(1) compatibility, ed runs in restricted mode if invoked 51 as red. This limits editing of files in the local directory only and 52 prohibits shell commands. 53 54DEVIATIONS 55---------- 561) Though ed is not a stream editor, it can be used to edit binary files. 57 To assist in binary editing, when a file containing at least one ASCII 58 NUL character is written, a newline is not appended if it did not 59 already contain one upon reading. In particular, reading /dev/null 60 prior to writing prevents appending a newline to a binary file. 61 62 For example, to create a file with ed containing a single NUL character: 63 $ ed file 64 a 65 ^@ 66 . 67 r /dev/null 68 wq 69 70 Similarly, to remove a newline from the end of binary `file': 71 $ ed file 72 r /dev/null 73 wq 74 752) Since the behavior of `u' (undo) within a `g' (global) command list is 76 not specified by POSIX, it follows the behavior of the SunOS ed: 77 undo forces a global command list to be executed only once, rather than 78 for each line matching a global pattern. In addition, each instance of 79 `u' within a global command undoes all previous commands (including 80 undo's) in the command list. This seems the best way, since the 81 alternatives are either too complicated to implement or too confusing 82 to use. 83 84 The global/undo combination is useful for masking errors that 85 would otherwise cause a script to fail. For instance, an ed script 86 to remove any occurrences of either `censor1' or `censor2' might be 87 written as: 88 ed - file <<EOF 89 1g/.*/u\ 90 ,s/censor1//g\ 91 ,s/censor2//g 92 ... 93 943) The `m' (move) command within a `g' command list also follows the SunOS 95 ed implementation: any moved lines are removed from the global command's 96 `active' list. 97 984) If ed is invoked with a name argument prefixed by a bang (!), then the 99 remainder of the argument is interpreted as a shell command. To invoke 100 ed on a file whose name starts with bang, prefix the name with a 101 backslash. 102