Question

I’ve seen system calls with numbers in them. For example: xterm(1), efence(3). I wanted to know what does 1 and 3 or for that matter any other number in these system calls mean?

Answer 1

Those numbers are the section of the manual, from the man page on man:

   The standard sections of the manual include:

   1      User Commands

   2      System Calls

   3      C Library Functions

   4      Devices and Special Files

   5      File Formats and Conventions

   6      Games et. Al.

   7      Miscellanea

   8      System Administration tools and Deamons

You can specify which section of the manual you want by adding the section number before the page you are looking for, the default result will be the lowest numbered section with the entry you are looking for. For example man exec and man 1 exec will take you to the shell command, and man 3 exec will take you to the C library page.