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fsync(2) System Calls Manual fsync(2) NAME fsync - Writes changes in a file to permanent storage SYNOPSIS #include <unistd.h> int fsync ( int fildes ); STANDARDS Interfaces documented on this reference page conform to industry stan- dards as follows: fsync(): XPG4 Refer to the standards(5) reference page for more information about in- dustry standards and associated tags. PARAMETERS Specifies a valid open file descriptor. DESCRIPTION The fsync function causes system buffers containing a file's modified data and attributes to be written to permanent storage. The fsync function does not return until the operation has been completed. The fsync function provides file integrity, ensuring that data and file at- tribute information in permanent storage is identical to data and file attribute information in the buffer. NOTES The file identified by the fildes parameter must be open for writing when the fsync function is issued or the call will fail. RETURN VALUES Upon successful completion, the fsync function returns a value of 0 (zero). If the fsync function fails, a value of -1 is returned and er- rno is set to indicate the error. If fsync fails, outstanding I/O oper- ations are not guaranteed to have been completed. ERRORS If the fsync function fails, errno may be set to one of the following values: [EBADF] The fildes parameter is not a valid file descriptor. [EINVAL] The fildes parameter does not refer to a file on which this operation is possible. If any queued I/O operations fail, the fsync function returns error conditions defined for the read and write functions. RELATED INFORMATION Functions: aio_fsync(2), fdatasync(2), fcntl(2), open(2), read(2), sync(2), write(2) Standards: standards(5) delim off fsync(2)