A close system call is a

system call In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, acc ...

used to close a

file descriptor In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier (handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typically have ...

by the

kernel Kernel may refer to: Computing * Kernel (operating system), the central component of most operating systems * Kernel (image processing), a matrix used for image convolution * Compute kernel, in GPGPU programming * Kernel method, in machine learnin ...

. For most

file systems In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

, a

program Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * Program, a part of planning Arts and entertainment Audio * Progra ...

terminates access to a

file File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to ''remove'' fine amounts of material from a workpiece **Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gent ...

in a filesystem using the close system call. This flushes file buffers, updates file

metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...

, which may include and

end-of-file In computing, end-of-file (EOF) is a condition in a computer operating system where no more data can be read from a data source. The data source is usually called a file or stream. Details In the C standard library, the character reading functio ...

indicator in the data; de-allocates resources associated with the file (including the

) and updates the system wide table of files in use. Some

programming languages A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

maintain a

data structure In computer science, a data structure is a data organization, management, and storage format that is usually chosen for efficient access to data. More precisely, a data structure is a collection of data values, the relationships among them, a ...

of files opened by their

runtime library In computer programming, a runtime library is a set of low-level routines used by a compiler to invoke some of the behaviors of a runtime environment, by inserting calls to the runtime library into compiled executable binary. The runtime enviro ...

and may close when the program terminates. This practice is known as resource acquisition is initialization (RAII). Some operating systems will invoke the close on files held by a program if it terminates. Some operating systems will invoke the close syscall as part of an operating system recovery as a result of a system failure.

C library POSIX definition

The
close
call is standardized by the

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...

specification int close (int filedes); int fclose (FILE *stream); The function returns zero to indicate the file was closed successfully. If any error occurs, a value of -1 is returned and errno is appropriately set. The errors that can occur include: ; : The argument supplied was not a valid file descriptor ; : The function call was interrupted by a

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...

; : An I/O error occurred

References

POSIX close

External links

* {{Computer files C POSIX library System calls