Sections

From Linux Man Pages

Sections are used to divide all available commands into categories. Some commands/names exist in multiple sections due to the command itself, its files and maybe a corresponding library implementation. Examples are

1. the crontab command: crontab(1) and the crontab file format: crontab (5)
2. the passwd command: passwd(1) and the passwd file: passwd(4)
3. exit functions: exit(3) library function and exit(2) kernel call

      1   User Commands: executable programs or shell commands
      2   System calls: functions provided by the kernel
      3   Library calls: functions provided by user libraries
      4   Devices and Special files (usually found in /dev)
      5   File format descriptions and conventions, e.g. /etc/passwd
      6   Games et.al
      7   Miscellaneous  (including  macro  packages and conventions), e.g. man(7), groff(7)
      8   System administration tools (in general only for root)
      9   Place for kernel routine documentation((Linux specific, Non standard)