intro_prm5(5) intro_prm5(5)
NAME
introprm5 - introduction to header files
DESCRIPTION
This chapter describes a number of header files whose contents may be
of interest to C programmers.
Header files are also often referred to as include files.
Header files contain the definition of symbolic constants, common
structures, preprocessor macros and predefined types. Each function
description specifies the header that an application must include in
order to use that function. If more than one header needs to be
included, this must also be specified. The header files must be
present on the system when the C source code is compiled. They need
not be present when the programs are executed.
The header files generally reside in the directory /usr/include or
/usr/include/sys. The directives #include <filename.h> or #include
<sys/filename.h> should be used to link the header files into C pro-
grams.
The following header files are new in XPG4:
fnmatch.h
glob.h
iconv.h
monetary.h
regex.h
wchar.h
wordexp.h
NOTES
The descriptions of the header files comply with X/Open specifica-
tions. Proprietary enhancements are not always included.
When you invoke man, you specify the names of the header files without
the .h ending, e.g. man unistd for the <unistd.h> header file. Like-
wise, the component sys can be omitted if it is part of the path, e.g.
man types for the <sys/types.h> header file.
Caution: For the time.h header file, you have to invoke either
man time for <time.h> or man systime for <sys/time.h>.
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