# phpman > man > mh-folders(5mh) [MH-FOLDERS(5mh)](https://www.chedong.com/phpMan.php/man/MH-FOLDERS/5mh/markdown) [MH-FOLDERS(5mh)](https://www.chedong.com/phpMan.php/man/MH-FOLDERS/5mh/markdown) ## NAME mh-folders - storage format used by nmh message system ## DESCRIPTION **nmh** stores messages in the files and directories of the host filesystem according to the fol‐ lowing rules: ### one folder per directory An **nmh** folder corresponds to a directory. There are no limits on folder names beyond those of the host filesystem. ### one message per file The file name is a positive integer. Other files containing metadata or arbitrary names can exist in a folder; while the preference is that non-message files begin with “.”, all files that are not positive integers _must_ be ignored by an **MH**-compatible implementa‐ tion. However, implementations are free to indicate to the user the existence of non- message files that are not prefixed with a “.”. The filename for a new message is one greater than the highest numbered message in the folder; its full path can be accessed by the pseudo-sequence _new_ (e.g., **mhpath** _new_). New messages are _only_ permitted to be added to a folder at the end of the message number range. To add a new message to a folder, the recommended sequence is: • Create a temporary file in the desired folder. • Attempt to link the temporary file to the new message number. • If successful, remove the temporary file. If the link fails, increment the message number and try again. ### context There is one context file. Its default location is in the user's Path and its default name is _context_, but these can be overridden by the $MHCONTEXT environment variable. **context** has the following format: **Current-Folder:** **+**_folder_ **atr-**_sequence-path_**:** _m[-n]_ _[...]_ where _folder_ is the directory name of the current folder. Lines beginning with “atr” are used for private sequences. _sequence_ is the name of the private sequence, _path_ is the full path to the folder with the private sequence, and _m[-n]_ is a message number or range of message numbers in the sequence. ### sequences There is one sequences file in each **nmh** folder. Its default name is _.mh_sequences_, but this can be overridden by the “mh-sequences” profile entry. **sequences** has the following format: **sequence:** _m[-n]_ _[...]_ showing the (possibly empty) message numbers and/or ranges of message numbers in each sequence. The **cur** sequence has at most just a single message number, not a range. Sequence names have a maximum size of 998 characters. Each line is also limited to a maximum of 998 characters, but RFC 822 continuation rules apply; sequences can be con‐ tinued across multiple lines by prefixing continuation lines with a whitespace charac‐ ter. If an implementation finds messages in a sequence that do not exist, the sequence file should be updated to remove the missing messages from the sequence. If a sequence con‐ tains no messages, it should be removed from the sequence file. The exception to this is the **cur** sequence, which can refer to a nonexistent message. ### Locking **nmh** programs read and write the context and sequences files, and lock these files when ac‐ cessing them. There should not be a need to access these files directly; instead, programs such as **flist**, **folder**, **mark**, **pick**, and **rcvstore** should be used to query and update their con‐ tents. Any program outside of **nmh** that accesses these files must be sure to lock them using the same locking method as **nmh**. The default data locking method is selected when **nmh** is con‐ figured and can be accessed as a string using **mhparam** **datalocking**. By default, fcntl locking is used, but this may be overridden by the **datalocking** profile entry. A second, possibly different, locking method is used by [**inc**(1)](https://www.chedong.com/phpMan.php/man/inc/1/markdown) when accessing the user's mail spool file or by **nmh** programs that open any mbox file. This locking method can be overridden when **nmh** is configured, or in the **nmh** mts configuration file, and can be accessed as a string using **mhparam** **spoollocking**. By default, kernel-level locking is used if appropriate for the platform, and it is for popular platforms. That default should also be the same as used by the **mail** program, if provided on the platform. ### Naming **nmh** folders can be given arbitrary names, with one exception: folders should not be given all-numeric names. This limitation results from **nmh** messages themselves being stored in nu‐ merically named files -- allowing folders to be named similarly would make **nmh** slower, and introduce usage ambiguities. ## FILES /context The user's context. $MHCONTEXT Overrides the above context. /.mh-sequences Public sequences for . ## SEE ALSO [_flist_(1)](https://www.chedong.com/phpMan.php/man/flist/1/markdown), [_folder_(1)](https://www.chedong.com/phpMan.php/man/folder/1/markdown), [_mail_(1)](https://www.chedong.com/phpMan.php/man/mail/1/markdown), [_mark_(1)](https://www.chedong.com/phpMan.php/man/mark/1/markdown), [_mhparam_(1)](https://www.chedong.com/phpMan.php/man/mhparam/1/markdown), [_mhpath_(1)](https://www.chedong.com/phpMan.php/man/mhpath/1/markdown), [_mh-profile_(5)](https://www.chedong.com/phpMan.php/man/mh-profile/5/markdown), [_mh-sequence_(5)](https://www.chedong.com/phpMan.php/man/mh-sequence/5/markdown), [_mh-tailor_(5)](https://www.chedong.com/phpMan.php/man/mh-tailor/5/markdown), [_pick_(1)](https://www.chedong.com/phpMan.php/man/pick/1/markdown), [_rcvstore_(1)](https://www.chedong.com/phpMan.php/man/rcvstore/1/markdown) nmh-1.7.1 2016-02-25 [MH-FOLDERS(5mh)](https://www.chedong.com/phpMan.php/man/MH-FOLDERS/5mh/markdown)