.TH "h5unjam" 1
.SH NAME
h5unjam \- Extract the user block from a HDF5 file
.SH SYNOPSIS
.B h5unjam
.B -i
.I in_file.h5
.RB [ -u
.I user_block
|
.BR --delete ]
.RB [ -o
.IR out_file.h5 ]
.SH DESCRIPTION
.B h5unjam 
splits an HDF5 file, writing the user block to a file or stdout and the
HDF5 file to an HDF5 file with a header at byte 0 (i.e., with no user
block).
.P
If
.I out_file.h5
is given, a new file is created with the
.I in_file.h5
without the user block. In this case,
.I infile.h5
is unchanged.
.P
If
.I out_file.h5
is not specified, the
.I user_block
is removed and
.I in_file.h5
is rewritten, starting at byte 0.
.P
If
.I user_block
is set, the user block will be written to 
.IR user_block .
If
.I user_block
is not set, the user block (if any) will be written to
stdout. If 
.B --delete
is selected, the user block will not be not written. 
.SH EXAMPLE USAGE
For an HDF5 file, 
.IR with_ub.h5 ,
with a user block, extract the user block to 
.I user_block.txt 
and the HDF5 file to
.IR wo_ub.h5 .
.P
	h5unjam -i with_ub.h5 -u user_block.txt -i wo_ub.h5
.SH RETURN VALUE
.B h5unjam
returns the size of the output file, or -1 if an error occurs.
.SH CAVEATS
This tool copies all the data (sequentially) in the file(s) to new
offsets. For a large file, this copy will take a long time.
.P
The most efficient way to create a user block is to create the
file with a user block (see
.BR H5Pset_user_block ),
and write the user block data into that space from a program.
.P
The user block is completely opaque to the HDF5 library and
to the
.B h5jam
and
.B h5unjam
tools.  The user block is simply read or written as a string of bytes,
which could be text or any kind of binary data.  It is up to the user 
to know what the contents of the user block means and how to process it.
.P
When the user block is extracted, all the data is
written to the output, including any padding or
unwritten data.
.P
This tool moves the HDF5 file through byte copies,
i.e., it does not read or interpret the HDF5
objects.
.SH "SEE ALSO"
\&\fIh5dump\fR\|(1), \fIh5ls\fR\|(1), \fIh5diff\fR\|(1),
\&\fIh5import\fR\|(1), \fIgif2h5\fR\|(1), \fIh52gif\fR\|(1),
\fIh5perf\fR\|(1), \fIh5jam\fR\|(1).