The manual pages

What are they?

Unix manual pages are there to provide explanations and help about Unix commands. We use manual pages to know how to use a C or Tk function... They are simple text files written in a special syntax to implement text formatting when they are displayed with the man command.

It is very convenient because they are often well detailed, but they actually have a lot of drawbacks: there are no or few examples, explanations are complete but usually not understandable for ordinary users and there are no really efficient search tool for these pages.

On the local hard drive, manual pages are stored in subdirectories of /usr/man/ or /usr/local/man/, each of them corresponds to a section of the manual pages (man1, man2...). It is then possible to find a page by browsing these directories. The main directory usually contains a whatis file that contains a short description of every Unix manual page.

How to use them

To read a manual page, we use the man command:

will display the manual page for the command called 'foo'.

We can often read something like this in the manual pages: crontab(5). This means that a dedicated manual page can be found for this command in the section number 5. One should them type:

to access this page.

This system is close to be perfect, but there are subtleties: a manual page can hide another one. There are indeed several manual pages that have the same name but that are not located in the same section. When we ask man to display a page without specifying the section, it displays the first page it has found. For instance, man crontab would display the manual page, section 1, for crontab, but the page of the section 5 is much more complete and interesting... To get rid of this behaviour, we can use the -a option:

to display successively all relevant manual pages for crontab.

This short explanation should be enough to start with manual pages. Anyway, for further information about man, please see the relevant manual page man(1) (do man man).

References

• man(1)
• complete list of Unix man pages

 printable format