C in a Nutshell, 2nd Edition

Chapter 18. Standard Library Functions

This chapter describes in alphabetical order the functions available in the standard ANSI C libraries. Most of the functions described here were included in the 1989 ANSI standard or in the 1995 “Normative Addendum” and are currently supported by all major compilers. The ISO/IEC 9899:1999 standard (“C99”) introduced several new functions, which are also widely supported by today’s compilers. The same cannot be said of the new, mostly optional features, such as multithreading and bounds-checking functions, introduced by the new ISO/IEC standard 9899:2011. The new functions introduced in that standard are labeled “C11” in this chapter.

Each description includes the function’s purpose and return value, the function prototype, the header file in which the function is declared, and a brief example. For the sake of brevity, the examples do not always show a main() function or the #include directives that indicate the header file with the function’s declaration. When using the functions described in this chapter, remember that you must provide a declaration of each standard function used in your program by including the appropriate header file. Also, any filename may also contain a relative or absolute directory path. For more information about errors and exceptions that can occur in standard function calls, see the sections on the standard headers math.h, fenv.h, and errno.h in Chapter 16.

In C11 implementations that support the “secure” alternative ...