`ed' is a line-oriented text editor. It is used to create, display,
modify and otherwise manipulate text files. `red' is a restricted `ed':
it can only edit files in the current directory and cannot execute
If invoked with a FILE argument, then a copy of FILE is read into
the editor's buffer. Changes are made to this copy and not directly to
FILE itself. Upon quitting `ed', any changes not explicitly saved with
a `w' command are lost.
Editing is done in two distinct modes: "command" and "input". When
first invoked, `ed' is in command mode. In this mode commands are read
from the standard input and executed to manipulate the contents of the
editor buffer. A typical command might look like:
which replaces all occurences of the string OLD with NEW.
When an input command, such as `a' (append), `i' (insert) or `c'
(change), is given, `ed' enters input mode. This is the primary means
of adding text to a file. In this mode, no commands are available;
instead, the standard input is written directly to the editor buffer. A
"line" consists of the text up to and including a <newline> character.
Input mode is terminated by entering a single period (`.') on a line.
All `ed' commands operate on whole lines or ranges of lines; e.g.,
the `d' command deletes lines; the `m' command moves lines, and so on.
It is possible to modify only a portion of a line by means of
replacement, as in the example above. However even here, the `s'
command is applied to whole lines at a time.
In general, `ed' commands consist of zero or more line addresses,
followed by a single character command and possibly additional
parameters; i.e., commands have the structure:
The ADDRESSes indicate the line or range of lines to be affected by
the command. If fewer addresses are given than the command accepts,
then default addresses are supplied.
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