man2

Man2 refers to the second section of the Unix manual. In Unix and Unix-like systems, manual pages are organized into numbered sections. Section 2 is dedicated to system calls, the low-level interfaces through which user-space programs request services from the kernel. Pages in this section describe kernel-provided functions as they appear to applications, including the function name, a short description, a prototype, parameters, return value, and possible errno values. They may also include notes on behavior, thread-safety, and portability, as well as related system calls.

Typical pages show a description, a synopsis with the function signature, a detailed description of arguments, the return value, an errors section listing errno values, and a see also section that references related entries in other sections (for example library wrappers in section 3). The exact content and format vary by OS and version, and some systems annotate calls with historical or behavioral caveats.

Using it: you can read a specific system call manual with 'man 2 open' or 'man 2 read', or browse a list with 'man 2' to see all entries. You can search the manual with 'man -k keyword' or 'apropos keyword'. On Linux, the pages live in /usr/share/man/man2; on BSD/macOS they exist under a similar path. Because section 2 content is kernel-facing, some calls differ or are absent on non-Linux systems, and 32-bit vs 64-bit ABIs can affect prototypes.

Historical note: man2 is part of the broader manual hierarchy that includes sections such as 1 for user commands and 3 for library functions. Understanding the section number is essential to disambiguate similarly named entries.