Problem using multiple 'head' commands in shell script
Kris Stephens [Hail Eris!]
krs at uts.amdahl.com
Sat Feb 2 03:01:51 AEST 1991
In article <1678 at abekrd.UUCP> garyb at abekrd.UUCP (Gary Bartlett) writes:
>*** FLASH OF INSPIRATION ***
>
>I have an idea:
>- Process the original file by putting the line number at the beginning of
> each line,
>- Process the file to be merged so that the merge points are at the beginning
> of each of these lines,
>- Cat the two processed files together and pass through 'sort',
>- Remove line numbers from beginning of resulting file, QED
>
>This doesn't matter how big either file is.
>
>Thoughts?
Hmmm.... If you've got the blocks available on your disk to
handle a second copy of the file, read it once and break it
into (n) pieces of your required length, each. This would
use pretty much the same number of blocks of storage (plus
at most a block-per-chunk for fractional last blocks) and
some number of inodes (number of lines / lines per chunk).
--- multi-piece processing --
:
file=${1:-file}
lines=${2:-200}
base=Base
# awk will return the number of subsets it created
subsets=`awk '
NR == 1 {
i++
outfile = base "" i
print > outfile
next
}
NR % lines == 1 {
close outfile
i++
outfile = base "" i
print > outfile
next
}
{ print >> outfile }
END { close outfile; print i + 0 }' base=$base lines=$lines $file`
i=1
while [ $i -le $subsets ]
do
subset="$base$i"
cat $subset
rm $subset # Clean up now
echo "# End of block $i"
i=`expr $i + 1`
done > report # or pipe it to something else (lp?)
--- multi-piece processing ---
The perl-literate will undoubtedly say "If you're going to do this,
use perl instead", but so it goes... :-)
Anyhow, this reads the data twice (once to break it into pieces
of $lines; once to cat them into the report file).
>Thanks again for some very useful input,
>Gary
You're very welcome -- helps me stretch out my thinking, too.
...Kris
--
Kristopher Stephens, | (408-746-6047) | krs at uts.amdahl.com | KC6DFS
Amdahl Corporation | | |
[The opinions expressed above are mine, solely, and do not ]
[necessarily reflect the opinions or policies of Amdahl Corp. ]
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