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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BZEXE(1) General Commands Manual BZEXE(1)
NAME
bzexe - compress executable files in place
SYNOPSIS
bzexe [ name ... ]
DESCRIPTION
The bzexe 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 ``bzexe /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
bzip2(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
bzexe 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.
BZEXE(1)