UNIX for Dummies Questions & Answers

Just wondering: Can anyone tell me what is meant by the term 'interactive shell" or 'built-in commands' - for example, if I type 'man set' I get a page listing all the 'built in commands' but no explanation of what they are as a concept or what they do.

And while I'm here: I was wondering as well how I access different sections of the manual - I've noticed there is an -S argument to the command 'man' but I don't know how to use it - I tried man [command] -S(number) and don't get anything.

is that what you were looking for?

Code:

man -S 1 ls

"Interactive shell" is an instance of a shell (ksh/bash/csh/...) that interacts with the user, = where you enter commands. A non-interactive shell would be a shell started to run an automated script, eg. via cron/at

"Built-In commands" are commands defined by the shell for which it doesn't need to start a sub-process. Those mostly affect the internal state of the shell (like 'set -x'), environment variables (like export), or control flow (if/case/...). You can see if a command is a built-in by entering 'type <command>'

As for man page sections: the -S switch defines which sections man should search in for the command you specified, not the sections inside the man page. An example of man sections (from Linux):

Code:

       0   Header files (usually found in /usr/include)
       1   Executable programs or shell commands
       2   System calls (functions provided by the kernel)
       3   Library calls (functions within program libraries)
       4   Special files (usually found in /dev)
       5   File formats and conventions eg /etc/passwd
       6   Games
       7   Miscellaneous  (including  macro  packages and conven-
           tions), e.g. man(7), groff(7)
       8   System administration commands (usually only for root)
       9   Kernel routines [Non standard]

It doesn't know about any sections inside the page itself, as it just passes the content of the page through a formatter (groff/troff/...) and then into a pager (more/less/...). Think of it as HTML: Just because there's a <h1> tag somewhere the browser won't automatically generate an index, it's just a formatting instruction.

I think I get it. Maybe I didn't ask my question correctly (Unfortunately, I don't remember exactly how I entered the Section argument). If I read your answer correctly, then what you're saying is that a command doesn't have more than one entry in different sections -- so ls for example is only in one section of the man pages (section 1)?

Am I able to go to different sections of the man pages, and if so, how would I do it?

And, as an aside, I noticed one of the sections you listed was for games. Can you tell me what they are? I entered 'man games' and got nothing, so I guess there is no command called 'games' and instead it lists the games in a certain section.

not to be overly recursive, but 'man man' could help.

No, it's not possible to jump between sections (at least not with the command-line utility). The usual chain of processing isThe pager itself has no idea of man pages or any links between them. Sections are just a way to logically structure the many pages available.

As for the games: almost every distribution has a package 'bsd-games' (or similar), containing classics like fortune, atc, caesar, or trek. Those man pages would be placed in section 6.