ed

The ed utility is a line-oriented text editor that uses two modes: command mode and input mode . In command mode the input characters shall be interpreted as commands, and in input mode they shall be interpreted as text. See the EXTENDED DESCRIPTION section. Provide a default value for the internationalization variables that are unset or null. (See XBD Internationalization Variables for the precedence of internationalization variables used to determine the values of locale categories.) If set to a non-empty string value, override the values of all the other internationalization variables. Determine the locale for the behavior of ranges, equivalence classes, and multi-character collating elements within regular expressions. Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multi-byte characters in arguments and input files) and the behavior of character classes within regular expressions. Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and informative messages written to standard output. [XSI) ] ![[Option Start]]( Determine the location of message catalogs for the processing of LC MESSAGES. ![[Option End]]( The ed utility shall interrupt its current activity, write the string "? n" to standard output, and return to command mode (see the EXTENDED DESCRIPTION section). If the buffer is not empty and has changed since the last write, the ed utility shall attempt to write a copy of the buffer in a file. First, the file named ed.hup in the current directory shall be used; if that fails, the file named ed.hup in the directory named by the HOME environment variable shall be used. In any case, the ed utility shall exit without writing the file to the currently remembered pathname and without returning to command mode. Various editing commands and the prompting feature (see -p ) write to standard output, as described in the EXTENDED DESCRIPTION section. The output files shall be text files whose formats are dependent on the editing commands given. Addressing in ed relates to the current line. Generally, the current line is the last line affected by a command. The current line number is the address of the current line. If the edit buffer is not empty, the initial value for the current line shall be the last line in the edit buffer; otherwise, zero. Addresses can be followed by zero or more address offsets, optionally -separated. Address offsets are constructed as follows: A decimal number shall add the indicated number of lines to the address. Commands accept zero, one, or two addresses. If more than the required number of addresses are provided to a command that requires zero addresses, it shall be an error. Otherwise, if more than the required number of addresses are provided to a command, the addresses specified first shall be evaluated and then discarded until the maximum number of valid addresses remain, for the specified command. Any characters included between addresses, address separators, or address offsets shall be ignored. In the following list of ed commands, the default addresses are shown in parentheses. The number of addresses shown in the default shall be the number expected by the command. The parentheses are not part of the address; they show that the given addresses are the default. (followed by an explanatory message if help mode has been enabled via the H command) to standard output and shall continue in command mode with the current line number unchanged. The a command shall read the given text and append it after the addressed line; the current line number shall become the address of the last inserted line or, if there were none, the addressed line. Address 0 shall be valid for this command; it shall cause the appended text to be placed at the beginning of the buffer. The c command shall delete the addressed lines, then accept input text th