Name space

All identifiers mentioned in this manual, except environ, are defined in at least one header file (see also chapter “Functions and variables in alphabetical order”). If _XOPEN_SOURCE is defined, every header file may potentially define or declare identifiers that conflict with those of the application. The set of identifiers visible to an application consists of the identifiers included by means of the #include statement and the additional identifiers reserved by the implementation (see also the manuals "C Compiler" [3 (Related publications)] and "C/C++ Compiler" [4 (Related publications)]).