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What do the parentheses and number after a Linux command or C function mean?

I see that many utilities have a number in brackets after their name, for example ls(1) or symlink(7). What are these numbers called, and what do they reference?

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marked as duplicate by Mokubai, Sathya Sep 3 '11 at 14:29

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

    
I have always seen this but never cared to ask or find an answer to this. +1 for asking this question. –  Jeffrey Jose Dec 29 '10 at 8:09
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2 Answers 2

up vote 23 down vote accepted

The numbers refer to the manpage section the manpage belongs to:

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 conventions), e.g. man(7), groff(7)

8 System administration commands (usually only for root)

9 Kernel routines [Non standard]

(from man man :-) )

The reason for showing the section is mainly that there is often a manpage with the same name in more than one section, e.g. man(1) (the man command), and man(7) (the system of manual pages). Same for e.g. system calls (section 2,3) and commandline programs (section 1) with the same name, e.g. unlink.

BTW, you can use man -a to see man pages from all sections for a given search term.

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Thanks! I think my man files must be set up wrongly. When I try to find man in section 7, I just get "No entry for man in section 7 of the manual" - and man(1) only describes how to invoke the man executable. –  Douglas Oct 4 '10 at 23:30
    
Well, the set of man pages is not standarized, AFAIK. So maybe your OS / installations just chose a diferent set of man pages... . What OS are you on? –  sleske Oct 4 '10 at 23:33
    
The section numbers vary somewhat between unix variants. 1, 2 and 3 are firmly entrenched, others less so. The list given here is for Linux. Many systems have an intro man page in each section. –  Gilles Oct 5 '10 at 21:58
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If you're looking at the man page when you see these, they are the "section" in which to look. By default, man pulls up the first entry it finds for a given query. However, this can cause issues where you have an entry for crontab, the command, and crontab, the system file (the command is used to edit the file). By specifying the section you want, you can tell man which you're looking for. man man should give you a listing of the sections, and you can select one with man <section> <query>, such as man 1 ls.

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