31.6.2 Man Page Lookup

On Unix, the main form of on-line documentation was the manual page or man page. In the GNU operating system, we hope to replace man pages with better-organized manuals that you can browse with Info (see Misc Help). This process is not finished, so it is still useful to read manual pages.

You can read the man page for an operating system command, library function, or system call, with the M-x man command. It runs the man program to format the man page; if the system permits, it runs man asynchronously, so that you can keep on editing while the page is being formatted. (On MS-DOS and MS-Windows 3, you cannot edit while Emacs waits for man to finish.) The result goes in a buffer named ‘*Man topic*’. These buffers use a special major mode, Man mode, that facilitates scrolling and jumping to other manual pages. For details, type C-h m while in a man page buffer.

Each man page belongs to one of ten or more sections, each named by a digit or by a digit and a letter. Sometimes there are multiple man pages with the same name in different sections. To read a man page from a specific section, type ‘topic(section)’ or ‘section topic’ when M-x manual-entry prompts for the topic. For example, to read the man page for the C library function chmod (as opposed to a command of the same name), type M-x manual-entry <RET> chmod(2) <RET> (chmod is a system call, so it is in section ‘2’).

If you do not specify a section, the results depend on how the man program works on your system. Some of them display only the first man page they find. Others display all man pages that have the specified name, so you can move between them with the M-n and M-p keys¹. The mode line shows how many manual pages are present in the Man buffer.

By default, Emacs highlights the text in man pages. For a long man page, highlighting can take substantial time. You can turn off highlighting of man pages by setting the variable Man-fontify-manpage-flag to nil.

If you insert the text of a man page into an Emacs buffer in some other fashion, you can use the command M-x Man-fontify-manpage to perform the same conversions that M-x manual-entry does.

An alternative way of reading manual pages is the M-x woman command². Unlike M-x man, it does not run any external programs to format and display the man pages; instead it does the job in Emacs Lisp, so it works on systems such as MS-Windows, where the man program (and other programs it uses) are not generally available.

M-x woman prompts for a name of a manual page, and provides completion based on the list of manual pages that are installed on your machine; the list of available manual pages is computed automatically the first time you invoke woman. The word at point in the current buffer is used to suggest the default for the name the manual page.

With a numeric argument, M-x woman recomputes the list of the manual pages used for completion. This is useful if you add or delete manual pages.

If you type a name of a manual page and M-x woman finds that several manual pages by the same name exist in different sections, it pops up a window with possible candidates asking you to choose one of them.

By default, M-x woman looks for manual pages in the directories specified in the MANPATH environment variable. (If MANPATH is not set, woman uses a suitable default value, which can be customized.) More precisely, woman looks for subdirectories that match the shell wildcard pattern man* in each one of these directories, and tries to find the manual pages in those subdirectories. When first invoked, M-x woman converts the value of MANPATH to a list of directory names and stores that list in the woman-manpath variable. Changing the value of this variable is another way to control the list of directories used.

You can also augment the list of directories searched by woman by setting the value of the woman-path variable. This variable should hold a list of specific directories which woman should search, in addition to those in woman-manpath. Unlike woman-manpath, the directories in woman-path are searched for the manual pages, not for man* subdirectories.

Occasionally, you might need to display manual pages that are not in any of the directories listed by woman-manpath and woman-path. The M-x woman-find-file command prompts for a name of a manual page file, with completion, and then formats and displays that file like M-x woman does.

The first time you invoke M-x woman, it defines the Dired W key to run the woman-find-file command on the current line's file. You can disable this by setting the variable woman-dired-keys to nil. See Dired. In addition, the Tar-mode w key is define to invoke woman-find-file on the current line's archive member.

For more information about setting up and using M-x woman, see WoMan.