Shell Programming and Scripting

thanks for the reply......the code is working fine.....ur code is :

awk ' { if ( NR == 1 ) { head=substr($0,1,300);} else { last = substr($0,1,300);} arr[i++]=$0; }END{ printf "Header is : %-300s Trailer is : %-300s\n", head, last; for( x=1; x<i-1; x++) { print arr[x] } }' old_file > new_file


The problem remains still the same ......for example if there are 1000 rows, one header and one trailer.......it concatenates hearder and trailer in one line and then copies this along with other 1000 rows to new file.......thus cuasing a lot of I/O........i have millions of records in the file and cannot afford to transfer one million records just for the sake of 2 lines (i.e. header and trailer)................

Before this, i got this code:

awk ' { if ( NR == 1 ) { head=$0 } else { last = $0 } }END{ printf "%-300s %-300s\n", head, last }' old_file > new_file
sed '1d;$d' old_file >> new_file

the above code has the same problem that it appends all the data rows................pls note that output is coming fine in both cases but I am concerned about the performance................all we need to do is:

1-Get header in old file (say string1)
2-Get trailer in old fine (say string2)
3-concatenate string1 and string2 (say the result is string3)
4-update the header in old file with string3
5-delete the trailer in old file.

Thanks....

First command with just awk logically should take lesser time than the second one with both awk and sed as the file is parsed twice in the latter case.

ok that is fine but I was just concerned about the number of files created........there is one problem that I am getting one extra line (blank line) at the end of file...........why is so using this code:


awk ' { if ( NR == 1 ) { head=substr($0,1,149);} else { last = substr($0,1,149);} arr[i++]=$0; }END{ printf "%-149s %-149s\n", head, last; for( x=1; x<i-1; x++) { print arr[x] } }' file1>file2


When I open file2,I get one extra line.......?

This works fine for me.
is there any blank space between trailer and detailed record ?

The output I get is like this:


Header (plus) Trailer
Record1
Recrod2
...
...
Record n
(blank line here)

Everything is perfect except that why this blank line is appearing when we have removed the trailer in original file?I want the last line Record n.

The original file was like this:

Header
Record1
Recrod2
...
...
Record n
Trailer