Standard API

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 to be 100% compatible with the standards. For both many fundamental reasons (HelenOS is not a 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. In an increasing number of cases, a part of the legacy standard-compliant interfaces is replaced by HelenOS native ones.

Native Interfaces

• FilesystemAPITutorial
• NetworkAPITutorial
• StringAPI

Legacy Interfaces

dirent.h

Function	Based on	Std Compliant
closedir	POSIX-1.2001	mostly
opendir	POSIX-1-2001	mostly
readdir	POSIX-1.2001	mostly
rewinddir	POSIX-1.2001	mostly

stdio.h

Function	Based on	Std Compliant
clearerr	POSIX-1.2001, C89, C99	mostly
fclose	POSIX-1.2001, C89, C99	mostly
fdopen	POSIX-1.2001	mostly
feof	POSIX-1.2001, C89, C99	mostly
ferror	POSIX-1.2001, C89, C99	mostly
fflush	POSIX-1.2001, C89, C99	mostly
fgetc	POSIX-1.2001, C89, C99	mostly
fgets	POSIX-1.2001, C89, C99	mostly
fileno	POSIX-1.2001	mostly
fopen	POSIX-1.2001, C89, C99	mostly
fputc	POSIX-1.2001, C89, C99	mostly
fputs	POSIX-1.2001, C89, C99	mostly
fprintf	POSIX-1.2001, C89, C99	mostly
fread	POSIX-1.2001, C89, C99	mostly
freopen	POSIX-1.2001, C89, C99	mostly
fseek	POSIX-1.2001, C89, C99	mostly
ftell	POSIX-1.2001, C89, C99	mostly
fwrite	POSIX-1.2001, C89, C99	mostly
rewind	POSIX-1.2001, C89, C99	mostly
setvbuf	C89, C99	mostly
setbuf	C89, C99	mostly
vfprintf	POSIX-1.2001, C89, C99	mostly
ungetc	POSIX-1.2001, C89, C99	mostly

unistd.h

Implemented functions (items marked wit D have been removed in the development version):

Function	Based on	Std Compliant	Note
sleep	POSIX.1-2001	mostly
usleep	POSIX.1-2001	mostly	obsoleted and replaced by nanosleep in POSIX.1-2008