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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dos2unix(1)						      General Commands Manual						       dos2unix(1)

dos2unix - DOS/MAC to UNIX text file format converter SYNOPSYS
dos2unix [options] [-c convmode] [-o file ...] [-n infile outfile ...] Options: [-hkqV] [--help] [--keepdate] [--quiet] [--version] DESCRIPTION
This manual page documents dos2unix, the program that converts plain text files in DOS/MAC format to UNIX format. OPTIONS
The following options are available: -h --help Print online help. -k --keepdate Keep the date stamp of output file same as input file. -q --quiet Quiet mode. Suppress all warning and messages. -V --version Prints version information. -c --convmode convmode Sets conversion mode. Simulates dos2unix under SunOS. -o --oldfile file ... Old file mode. Convert the file and write output to it. The program default to run in this mode. Wildcard names may be used. -n --newfile infile outfile ... New file mode. Convert the infile and write output to outfile. File names must be given in pairs and wildcard names should NOT be used or you WILL lost your files. EXAMPLES
Get input from stdin and write output to stdout. dos2unix Convert and replace a.txt. Convert and replace b.txt. dos2unix a.txt b.txt dos2unix -o a.txt b.txt Convert and replace a.txt in ASCII conversion mode. Convert and replace b.txt in ISO conversion mode. Convert c.txt from Mac to Unix ascii format. dos2unix a.txt -c iso b.txt dos2unix -c ascii a.txt -c iso b.txt dos2unix -c mac a.txt b.txt Convert and replace a.txt while keeping original date stamp. dos2unix -k a.txt dos2unix -k -o a.txt Convert a.txt and write to e.txt. dos2unix -n a.txt e.txt Convert a.txt and write to e.txt, keep date stamp of e.txt same as a.txt. dos2unix -k -n a.txt e.txt Convert and replace a.txt. Convert b.txt and write to e.txt. dos2unix a.txt -n b.txt e.txt dos2unix -o a.txt -n b.txt e.txt Convert c.txt and write to e.txt. Convert and replace a.txt. Convert and replace b.txt. Convert d.txt and write to f.txt. dos2unix -n c.txt e.txt -o a.txt b.txt -n d.txt f.txt DIAGNOSTICS
The program does not work properly under MSDOS in stdio processing mode. If you know why is that so, please tell me. AUTHORS
Benjamin Lin - <> Bernd Johannes Wuebben (mac2unix mode) <> MISCELLANY
Tested environment: Linux 1.2.0 with GNU C 2.5.8 SunOS 4.1.3 with GNU C 2.6.3 MS-DOS 6.20 with Borland C++ 4.02 Suggestions and bug reports are welcome. SEE ALSO
unix2dos(1) mac2unix(1) 1995.03.31 dos2unix v3.0 dos2unix(1)