This document serves as an overview of HelenOS standard user space API implemented in HelenOS C library and the relation of this API to common standards such as "C Standard Library" (as defined by various ISO C standards, such as C99) and C POSIX Library standards.

General note: The primary aim of HelenOS C library is not a to be 100% compatible with the standards. For both many fundamental reasons (HelenOS is not an unix-like operating system) and practical reasons (our subjective dislike of some aspects of the standards, security issues, etc.) the HelenOS C library follows the standards very loosely. Many functions are not implemented because lack of current need or simple because lack of manpower and many functions closely resemble their standard-compliant counterparts, but behave very slightly differently.

unistd.h

Implemented functions:

Function	Based on	Std Compliant	Note
chdir	POSIX-1-2001	mostly
close	POSIX-1.2001	mostly
dup2	POSIX-1.2001	mostly
exit	POSIX-1.2001, C89, C99	mostly	should be defined in stdlib.h by POSIX
fsync	POSIX.1-2001	partially	non-standard semantics
ftruncate	POSIX.1-2001	partially	the absolute offset is aoff64_t
getcwd	POSIX.1-2001	mostly
lseek	POSIX.1-2001	partially	relative offset is off64_t
read	POSIX.1-2001	mostly
rmdir	POSIX.1-2001	mostly
sleep	POSIX.1-2001	mostly
unlink	POSIX.1-2001	mostly
usleep	POSIX.1-2001	mostly	obsoleted and replaced by nanosleep in POSIX.1-2008
write	POSIX.1-2001	mostly

Unimplemented functions:

TBD