# PetscBinaryWrite
Writes to a binary file. 
## Synopsis
```
PetscErrorCode PetscBinaryWrite(int fd, const void *p, PetscInt n, PetscDataType type)
```
Not Collective


## Input Parameters

- ***fd     -*** the file
- ***p      -*** the buffer
- ***n      -*** the number of items to write
- ***type   -*** the type of items to read (`PETSC_INT`, `PETSC_REAL` or `PETSC_SCALAR`)





## Notes
`PetscBinaryWrite()` uses byte swapping to work on all machines; the files
are written using big-endian ordering to the file. On little-endian machines the numbers
are converted to the big-endian format when they are written to disk.
When PETSc is ./configure with --with-64-bit-indices the integers are written to the
file as 64 bit integers, this means they can only be read back in when the option --with-64-bit-indices
is used.

If running with __float128 precision the output is in __float128 unless one uses the -binary_write_double option

The Buffer p should be read-write buffer, and not static data.
This way, byte-swapping is done in-place, and then the buffer is
written to the file.

This routine restores the original contents of the buffer, after
it is written to the file. This is done by byte-swapping in-place
the second time.

Because byte-swapping may be done on the values in data it cannot be declared const


## See Also
 `PetscBinaryRead()`, `PetscBinaryOpen()`, `PetscBinaryClose()`, `PetscViewerBinaryGetDescriptor()`, `PetscBinarySynchronizedWrite()`,
`PetscBinarySynchronizedRead()`, `PetscBinarySynchronizedSeek()`

## Level
advanced

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/fileio/sysio.c.html#PetscBinaryWrite">src/sys/fileio/sysio.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex6.c.html">src/vec/vec/tutorials/ex6.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/vec/vec/tutorials/ex6f.F90.html">src/vec/vec/tutorials/ex6f.F90.html</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/fileio/sysio.c)


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