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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 REDHAT

gzexe

GZEXE(1)						      General Commands Manual							  GZEXE(1)

NAME

       gzexe - compress executable files in place

SYNOPSIS

       gzexe [ name ...  ]

DESCRIPTION

       The  gzexe  utility  allows you to compress executables in place and have them automatically uncompress and execute when you run them (at a
       penalty in performance).  For example if you execute ``gzexe /bin/cat'' it will create the following two files:
	   -r-xr-xr-x  1 root  bin   9644 Feb 11 11:16 /bin/cat
	   -r-xr-xr-x  1 bin   bin  24576 Nov 23 13:21 /bin/cat~
       /bin/cat~ is the original file and /bin/cat is the self-uncompressing executable file.  You can remove /bin/cat~ once  you  are	sure  that
       /bin/cat works properly.

       This utility is most useful on systems with very small disks.

OPTIONS

       -d     Decompress the given executables instead of compressing them.

SEE ALSO

       gzip(1), znew(1), zmore(1), zcmp(1), zforce(1)

CAVEATS

       The  compressed	executable  is a shell script. This may create some security holes. In particular, the compressed executable relies on the
       PATH environment variable to find gzip and some other utilities (tail, chmod, ln, sleep).

BUGS

       gzexe attempts to retain the original file attributes on the compressed executable, but you may have to fix them manually  in  some  cases,
       using chmod or chown.

																	  GZEXE(1)
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