# PetscViewerASCIIOpen
Opens an ASCII file for writing as a `PetscViewer`. 
## Synopsis
```
#include "petscviewer.h"   
PetscErrorCode PetscViewerASCIIOpen(MPI_Comm comm, const char name[], PetscViewer *lab)
```
Collective


## Input Parameters

- ***comm -*** the communicator
- ***name -*** the file name



## Output Parameter

- ***lab -*** the PetscViewer to use with the specified file





## Notes
To open a ASCII file as a viewer for reading one must use the sequence
```none
   PetscViewerCreate(comm,&lab);
   PetscViewerSetType(lab,PETSCVIEWERASCII);
   PetscViewerFileSetMode(lab,FILE_MODE_READ);
   PetscViewerFileSetName(lab,name);
```


This `PetscViewer` can be destroyed with `PetscViewerDestroy()`.

The MPI communicator used here must match that used by the object one is viewing. For example if the
Mat was created with a `PETSC_COMM_WORLD`, then the Viewer must be created with `PETSC_COMM_WORLD`

As shown below, `PetscViewerASCIIOpen()` is useful in conjunction with
`MatView()` and `VecView()`
```none
     PetscViewerASCIIOpen(PETSC_COMM_WORLD,"mat.output",&viewer);
     MatView(matrix,viewer);
```



## See Also
 `MatView()`, `VecView()`, `PetscViewerDestroy()`, `PetscViewerBinaryOpen()`, `PetscViewerASCIIRead()`, `PETSCVIEWERASCII`
`PetscViewerASCIIGetPointer()`, `PetscViewerPushFormat()`, `PETSC_VIEWER_STDOUT_`, `PETSC_VIEWER_STDERR_`,
`PETSC_VIEWER_STDOUT_WORLD`, `PETSC_VIEWER_STDOUT_SELF`,

## Level
beginner

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/classes/viewer/impls/ascii/vcreatea.c.html#PetscViewerASCIIOpen">src/sys/classes/viewer/impls/ascii/vcreatea.c</A>

## Examples
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex54.c.html">src/ksp/ksp/tutorials/ex54.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex55.c.html">src/ksp/ksp/tutorials/ex55.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex56.c.html">src/ksp/ksp/tutorials/ex56.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ksp/ksp/tutorials/ex72.c.html">src/ksp/ksp/tutorials/ex72.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex15.c.html">src/snes/tutorials/ex15.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex1f.F90.html">src/snes/tutorials/ex1f.F90.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex48.c.html">src/snes/tutorials/ex48.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/snes/tutorials/ex70.c.html">src/snes/tutorials/ex70.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/tutorials/ex14.c.html">src/ts/tutorials/ex14.c.html</A><BR>
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/ts/tutorials/ex9.c.html">src/ts/tutorials/ex9.c.html</A><BR>


---
[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/classes/viewer/impls/ascii/vcreatea.c)


[Index of all Viewer routines](index.md)  
[Table of Contents for all manual pages](/docs/manualpages/index.md)  
[Index of all manual pages](/docs/manualpages/singleindex.md)  
