Man is the system's Manual pager.
The table below shows the section numbers of the manual followed by the types of pages they contain.
1 executable programs or shell commands
2 system CILS (functions provided by the kernel)
3 Library CILS (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]
If you don't install man (2/3), please run "sudo apt-Get install manpages-dev ".
Man 2/3 is very useful, for example:
1) MAN 2 Write
Write (2) Linux programmer's Manual write (2)
Name
Write-write to a file descriptor
Synopsis
# Include <unistd. h>
Ssize_t write (int fd, const void * Buf, size_t count );
Description
.......