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How to retain the header information of a file

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Old 12-04-2007
How to retain the header information of a file


I am using Bash shell to create some data and these data would be piped out to a file, let say output.txt.

This output.txt I would like to add some extra header information such as comments, descriptions and general information on the text.

I would like to know how could I maintain this type of information. I did try out using append to a file. In other word,I created a file with initial description and comments on it. Then, these data I would append (using << output.txt).

However, one limitation of this is that the data would be keep adding on top of the file each time repeated command are executed. Anyone have idea to solve this?

Besides, another problem is by having this header, I would like to further extract the data from the output.txt without the description and comments. I tried using head and tail but it doesnt work automatically. In other words, let say description and comment I have as first 5 lines of the output.txt. Currently I extract out these data using cat output.txt|..<all the operation>. But I could not help but extracting the first 5 lines as well.

Please advise. Appreciate alot.


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h5jam(1)						      General Commands Manual							  h5jam(1)

h5jam - Add a user block to a HDF5 file SYNOPSIS
h5jam -u user_block -i in_file.h5 [-o out_file.h5] [--clobber] DESCRIPTION
h5jam concatenates a user_block file and an HDF5 file to create an HDF5 file with a user block. The user block can be either binary or text. The output file is padded so that the HDF5 header begins on byte 512, 1024, etc.. (See the HDF5 File Format.) If out_file.h5 is given, a new file is created with the user_block followed by the contents of in_file.h5. In this case, infile.h5 is unchanged. If out_file.h5 is not specified, the user_block is added to in_file.h5. If in_file.h5 already has a user block, the contents of user_block will be added to the end of the existing user block, and the file shifted to the next boundary. If --clobber is set, any existing user block will be overwritten. EXAMPLE USAGE
Create new file, newfile.h5, with the text in file mytext.txt as the user block for the HDF5 file file.h5. h5jam -u mytext.txt -i file.h5 -o newfile.h5 Add text in file mytext.txt to front of HDF5 dataset, file.h5. h5jam -u mytext.txt -i file.h5 Overwrite the user block (if any) in file.h5 with the contents of mytext.txt. h5jam -u mytext.txt -i file.h5 --clobber RETURN VALUE
h5jam returns the size of the output file, or -1 if an error occurs. 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. The most efficient way to create a user block is to create the file with a user block (see H5Pset_user_block), and write the user block data into that space from a program. The user block is completely opaque to the HDF5 library and to the h5jam and 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. When the user block is extracted, all the data is written to the output, including any padding or unwritten data. This tool moves the HDF5 file through byte copies, i.e., it does not read or interpret the HDF5 objects. SEE ALSO
h5dump(1), h5ls(1), h5diff(1), h5import(1), gif2h5(1), h52gif(1), h5perf(1), h5unjam(1). h5jam(1)

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