55 lines
2.9 KiB
Plaintext
55 lines
2.9 KiB
Plaintext
This version of ed is not strictly POSIX compliant, as described in the
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POSIX 1003.2 Draft 11.2 document. BSD commands have been implemented
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wherever they do not conflict with the POSIX standard. For backwards
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compatibility, the POSIX rule that says a range of addresses cannot be
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used where only a single address is expected has been relaxed.
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The BSD commands included are:
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1) the `s' command (i.e., s[rgp]*) to repeat a previous substitution,
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2) the `W' command for appending text to an existing file,
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3) the `wq' command for exiting after a write, and
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4) the `z' command for scrolling through the buffer.
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BSD line addressing syntax (i.e., `^' and `%'). is also recognized.
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The POSIX interactive global commands `G' and `V' are extended to support
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multiple commands, including `a', `i' and `c'. The command format is the
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same as for the global commands `g' and `v', i.e., one command per line
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with each line, except for the last, ending in a backslash (\).
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If crypt is available, files can be read and written using DES encryption.
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The `x' command prompts the user to enter a key used for encrypting/
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decrypting subsequent reads and writes. If only a newline is entered as
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the key, then encryption is disabled. Otherwise, a key is read in the
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same manner as a password entry. The key remains in effect until
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encryption is disabled. For more information on the encryption algorithm,
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see the bdes(1) man page. Encryption/decryption should be fully compatible
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with SunOS DES.
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An extension to the POSIX file commands `E', `e', `r', `W' and `w' is that
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<file> arguments are processed for backslash escapes, i.e., any character
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preceded by a backslash is interpreted literally. A trailing backslash
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is ignored. If the first unescaped character of a <file> argument is a
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bang (!), then the rest of the line is interpreted as a shell command,
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and no escape processing is performed by ed. This rule does not apply to
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the 'f' command (described below).
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While the default file name cannot be set to a shell command (i.e.,
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!<shell-cmd>) via any of the `r', `w', and `e' commands, POSIX evidently
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does not preclude using the `f' command for this purpose. Upon reading
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or writing the default file when its name begins with a bang, ed
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interprets the rest of the line as a shell command and attempts to execute
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it. Escape processing is not performed in this case.
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If ed is invoked with a name argument prefixed by a bang, then the
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remainder of the argument is interpreted as a shell command. To invoke
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ed on a file whose name starts with bang, prefix the name with a backslash.
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--
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The following commands are neither part of POSIX 1003.2 D11/2 nor are
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they supported in this version of ed.
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The vi command: (addr1,addr2) !<shell-cmd> which replaces a range of
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lines with the output of a shell command is not supported.
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The vi command: [rwe] !!, where !! is replaced by the previous
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!<shell-cmd> is not supported.
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