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Full Discussion: use of sed over cat to merge files
Top Forums UNIX for Advanced & Expert Users use of sed over cat to merge files Post 302147767 by miwinter on Wednesday 28th of November 2007 11:25:33 AM
Old 11-28-2007
use of sed over cat to merge files
I have three files, basically:

file 1 - one line header
file 2 - big data (approx 80GB)
file 3 - a one line trailer

the existing process cats these together i.e cat file 1 file 2 file 3

however... I was thinking, surely it could be more efficient to insert the header (file 1) on the data file (file 2) and then just append the trailer (file 3) on the end.

I wondered if this could be achieved some way via sed instead, i.e. something like:

#!/bin/sh

export HEAD=`cat $1`
export TRAIL=`cat $3`

sed -e '1i\
$HEAD
$a\
$TRAIL' $2 > complete_file.txt

...but it seems this won't substitute in the variable values setup within the shell script already

Thanks in advance for any replies on this one.
Last edited by miwinter; 11-28-2007 at 01:24 PM..
 

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LEARN ABOUT DEBIAN

flow-merge

flow-merge(1)						      General Commands Manual						     flow-merge(1)

NAME

       flow-merge -- Merge flow files.

SYNOPSIS

       flow-merge [-aghm]  [-b big|little]  [-C comment]  [-d debug_level]  [-o filename]  [-z z_level]  [file|directory ...]

DESCRIPTION

       The  flow-merge	utility processes files and/or directories of files in the flow-tools format.  The resulting merged data set is written to
       the standard output or file specified by -o.  If file is a single dash (`-') or absent, flow-merge  will  read  from  the  standard  input.
       Unlike flow-cat, flow-merge interleaves flow records preserving the relative chronological order.

OPTIONS

       -a	 Do not ignore filenames that begin with tmp.

       -b big|little
		 Byte order of output.

       -C Comment
		 Add a comment.

       -d debug_level
		 Enable debugging.

       -g	 Sort file list by capture start time before processing.

       -h	 Display help.

       -m	 Disable the use of mmap().

       -p	 Preload headers.  Use to preserve meta information such as lost flows.

       -o file	 Write to file instead of the standard out.

       -z z_level
		 Configure compression level to  z_level.  0 is disabled (no compression), 9 is highest compression.

       file|directory...
		 Process the files and/or directory.

EXAMPLES

       Merge all flow files begining with ft-v05.2001-05.01, use flow-print to display the results.

	   flow-merge ft-v05.2001-05-01.* | flow-print

BUGS

       None known.

AUTHOR

       Larry Lidz ellidz@eridu.uchicago.edu

SEE ALSO

       flow-tools(1)

																     flow-merge(1)
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