fsync

Name

fsync - synchronizes a file's complete in-core state with that on disk

Library

libc.lib

Synopsis

#include <unistd.h>

int fsync (int fd);

Return values

.Rv -std fsync

Detailed description

The fsync system call causes all modified data and attributes of fd to be moved to a permanent storage device. This normally results in all in-core modified copies of buffers for the associated file to be written to a disk.

The fsync system call should be used by programs that require a file to be in a known state, for example, in building a simple transaction facility.

Examples

/**
  * Detailed description : Simple usage of fsync system call.
  * Preconditions : Example.txt if present should not a ready-only file
**/
#include <unistd.h>
#include <fcntl.h>
int main()
{
  int fd = 0;
  fd = open("Example.txt" , O_CREAT | O_RDWR , 0666);
  if(fd < 0 )  
  {
     printf("Failed to open file Example.txt \n");
     return -1;
  }
  if(fsync(fd) < 0 )  
  {
     printf("fsync system call failed \n");
     return -1;
  }
  close(fd);
  printf("fsync system call succeeded \n");
  return 0;
}

Output

fsync system call succeeded

Errors

The fsync fails if:

[`EBADF`]
	The fd argument is not a valid descriptor.
[`EINVAL`]
	The fd argument refers to a socket, not to a file.
[`EIO`]	An I/O error occurred while reading from or writing to the file system.