Editing C standard library (section)

=== POSIX standard library ===
{{Main article|C POSIX library}}

[[POSIX]], as well as [[Single Unix Specification|SUS]], specify a number of routines that should be available over and above those in the basic C standard library. The POSIX specification includes header files for, among other uses, [[POSIX Threads|multi-threading]], [[Berkeley sockets|networking]], and [[regular expression]]s. These are often implemented alongside the C standard library functionality, with varying degrees of closeness. For example, [[glibc]] implements functions such as <code>[[fork (operating system)|fork]]</code> within <code>libc.so</code>, but before [[NPTL]] was merged into glibc it constituted a separate library with its own linker flag argument. Often, this POSIX-specified functionality will be regarded as part of the library; the basic C library may be identified as the ANSI or [[International Organization for Standardization|ISO]] C library.