MH-ALIAS(5mh)

💖 NAME 💖

mh-alias — it's giving the format of nmh email-address alias files, and honestly? it's iconic. This is the MH-ALIAS(5mh) page, bestie, so buckle up. 🎀

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✨ DESCRIPTION ✨

okay so every single line of an nmh alias file is one of these four forms, no exceptions, periodt:

alias : address-group

alias ; address-group

< alias-file

; | : | # comment

and where those lil pieces come from:

address-group  := address-list
               |  < file

address-list   := address
               |  address-list, address

Continuation lines end with \ followed by a newline character. And yes this applies to comment lines too — so the line right after a \-terminated comment line is literally a continuation of that comment line. 💅

Alias-file and file are Unix file names. Alias file contents are case-insensitive, with the exception of filesystem path names (those stay picky, as they should 🫶).

If the line starts with a <, the file named after the < is read for more alias definitions. And the reading is done recursively, so a < may occur in the beginning of an alias file with the expected results. ✨

If the address-group starts with a <, the file named after the < is read and its contents are added to the address-list for the alias. 🦋

In match, a trailing * on an alias will match just about anything appropriate. slay.

An approximation of the way aliases are resolved at posting time is:

1. Build a list of all addresses from the message to be delivered, eliminating duplicate addresses.
2. For those addresses in the message that have no host specified, perform alias resolution.
3. For each line in the alias file, compare alias against all of the existing addresses. If a match, remove the matched alias from the address list, and add each new address in the address-group to the address list if it is not already on the list. The alias itself is not usually output, rather the address-group that the alias maps to is output instead. If alias is terminated with a ; instead of a :, then both the alias and the address are output in the correct format (with the alias quoted if necessary and the address wrapped in <>). 💅

Since the mh-alias file is read line by line, forward references work, but backward references are not recognized. not me finding out the hard way 😭

🌸 Example Alias File 🌸

</etc/nmh/BBoardAliases
sgroup: fred, fear, freida
fred: frated@UCI.example
b-people: Blind List: bill, betty
Unix-committee: <unix.aliases
news.*: news

The first line says that more aliases should immediately be read from the file /etc/nmh/BBoardAliases. Next, sgroup is defined as an alias for three names, and one of them, fred, is a forward reference to another alias for frated@UCI.example. 👑

The alias b-people is a blind list which includes the addresses bill and betty; the message will be delivered to those addresses, but the message header will show only Blind List: ; (not the addresses). The alias must not be terminated with, or contain, a semicolon. Note that blind lists are not supported with the sendmail/pipe mail transport method. 💀

The definition of Unix-committee is given by reading the file unix.aliases in the user's nmh directory. 🧚

Lastly, news.anything is aliased to news; the full stop is just another literal character. no cap.

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🎀 PROFILE COMPONENTS 🎀

• Aliasfile: — Default alias file. ✨

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🌈 FILES 🌈

• /etc/nmh/MailAliases — System-wide default alias file.

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🦋 SEE ALSO 🦋

ali(1), send(1), whom(1), getgrent(3), getpwent(3), post(8)

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💅 BUGS 💅

Although the forward-referencing semantics of mh-alias files prevent recursion, the alias-file directive may defeat this. Since the number of file descriptors is finite, such infinite recursion will terminate with a meaningless diagnostic when all the fds are used up. it's giving chaos, bestie 😭

Earlier versions of this man page showed a semicolon at the end of the blind list example. That caused the preceding alias to not be expanded. There must not be a semicolon at the end of, or within, the address group of a blind list. post will append the semicolon to the blind list name. 🙈

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okay that's the whole page, you ate it, go post some mail 💖

this was nmh-1.8, dated 2014-04-18 — mwah, xoxo, the manual page 💋