What does “on-line” mean, as used in man(1)

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On my system (Darwin 15.5.0), man(1) opens as follows:

NAME
       man - format and display the on-line manual pages

The file the page is formatted from, however, is clearly on disk:

% man -w man
/usr/share/man/man1/man.1
% file `man -w man`
/usr/share/man/man1/man.1: troff or preprocessor input text

So, "on-line" in this case does not mean "online," as in, "somewhere else accessible over the Internet."

Does "on-line" just mean that my system is powered on? If so, why bother specifying that in the first place, i.e., isn't it obvious that I'm reading a page that the formatter processed? Or, when the description was written, was it a huge deal to have a manual on disk because most "manuals" then were paper volumes? Is this usage of "on-line," hyphen and all, still common in computing?

Best Answer

In contrast to a printed (hard-copy) manual, which you could read off-line (while not using a computer).

The term dates back (at least) to time-sharing systems. Users may have had a terminal which could be used for typing text, punching paper tapes. But they were only able to use the computer when they were on-line (the "line" referring to the communications link from the terminal to the computer).

Lots of English is that way: you likely use terms which on reflection you might not consider up-to-date.

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man Pages – What Do the Numbers Mean?

The number corresponds to what section of the manual that page is from; 1 is user commands, while 8 is sysadmin stuff. The man page for man itself (man man) explains it and lists the standard ones:

MANUAL SECTIONS
    The standard sections of the manual include:

    1      User Commands
    2      System Calls
    3      C Library Functions
    4      Devices and Special Files
    5      File Formats and Conventions
    6      Games et. al.
    7      Miscellanea
    8      System Administration tools and Daemons

    Distributions customize the manual section to their specifics,
    which often include additional sections.

There are certain terms that have different pages in different sections (e.g. printf as a command appears in section 1, as a stdlib function appears in section 3); in cases like that you can pass the section number to man before the page name to choose which one you want, or use man -a to show every matching page in a row:

$ man 1 printf
$ man 3 printf
$ man -a printf

You can tell what sections a term falls in with man -k (equivalent to the apropos command). It will do substring matches too (e.g. it will show sprintf if you run man -k printf), so you need to use ^term to limit it:

$ man -k '^printf'
printf               (1)  - format and print data
printf               (1p)  - write formatted output
printf               (3)  - formatted output conversion
printf               (3p)  - print formatted output
printf [builtins]    (1)  - bash built-in commands, see bash(1)

Note that the section can sometimes include a subsection (e.g., the p in 1p and 3p above). The p subsection is for POSIX specifications; the x subsection is for X Window System documentation.

What format does man use

Give nroff a go, most recent versions of 'man' use *roff by default.

man man

Shows under Defaults that nroff is the default on my Ubuntu & OS X systems so should be a safe bet.

Best Answer

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man Pages – What Do the Numbers Mean?

What format does man use

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