15+  10/05 crocker     nned  <<Last week I asked some of
16-  10/05 crocker     message id format  <<I recommend
18   10/06 brien       Re: Exit status from mkdir
19   10/07*brien       ``scan'' listing format in nmh

The `+' on message 15 indicates that it is the current message.

The `-' on message 16 indicates that it has been replied to, as indicated by a ``Replied:'' component (produced by the -annotate switch to the repl command).

The `*' on message 19 indicates that no ``Date:'' header was present. The time of last modification of the message is given instead.

If there is sufficient room left on the scan line after the subject, the line will be filled with text from the body, preceded by ``<<'', and terminated by ``>>'' if the body is sufficiently short. Scan actually reads each of the specified messages and parses them to extract the desired fields. During parsing, appropriate error messages will be produced if there are format errors in any of the messages.

By default, scan will decode RFC 2047 (MIME) encoding in these scan listings. Scan will only decode these fields if your terminal can natively display the character set used in the encoding. You should set the appropriate locale(1) environment variables to your native character set, if it is not US-ASCII. See locale(1) for more details on the appropriate environment variables.

The switch -reverse, makes scan list the messages in reverse order.

The -file filename switch allows the user to obtain a scan listing of a maildrop file as produced by packf. This listing includes every message in the file (you can't scan individual messages). The switch -reverse is ignored with this option.

The switch -width columns may be used to specify the width of the scan line. The default is to use the width of the terminal.

The -header switch produces a header line prior to the scan listing. Currently, the name of the folder and the current date and time are output (see the HISTORY section for more information).

If the -clear switch is used and scan's output is directed to a terminal, then scan will consult the environment variables $TERM and $TERMCAP to determine your terminal type in order to find out how to clear the screen prior to exiting. If the -clear switch is used and scan's output is not directed to a terminal (e.g., a pipe or a file), then scan will send a formfeed prior to exiting.

For example, the command:

(scan -clear -header; show all -show pr -f) | lpr

produces a scan listing of the current folder, followed by a formfeed, followed by a formatted listing of all messages in the folder, one per page. Omitting ``-show pr -f'' will cause the messages to be concatenated, separated by a one-line header and two blank lines.

To override the output format used by scan, the -format string or -form file switches are used. This permits individual fields of the scan listing to be extracted with ease. The string is simply a format string and the file is simply a format file. See mh-format(5) for the details.

In addition to the standard mh-format(5) escapes, scan also recognizes the following additional component escapes:

Escape   Returns  Description
body      string   the (compressed) first part of the body
dtimenow  date     the current date
folder    string   the name of the current folder

If no date header is present in the message, the function escapes which operate on {date} will return values for the date of last modification of the message file itself. This feature is handy for scanning a draft folder, as message drafts usually aren't allowed to have dates in them.

The /etc/nmh directory contains several format files as examples of customized scan output.

scan will update the nmh context prior to starting the listing, so interrupting a long scan listing preserves the new context. nmh purists hate this idea.