Shell Programming and Scripting

I have a fixed with file with header & trailer length having the same length of the detail record file.

The details record length of this file is 24, for Header and Trailer the records will be padded with spaces to match the record length of the file
Currently I am adding 3 spaces in header and 6 spaces in trailer to match with detail record length

current value of my header is
Column Name Data length
---------- ----------

Code:

A        1
B        2
C        2
D        8
E        8

current value of my trailer is

Column Name Data length
---------- ----------

Code:

A        1
B        2
C        15

My requirement is to change the value of the second column(Column B) from xx to yyy both in header and trailer.
After this change I should have only two spaces in header and 5 spaces in trailer

Can some one help here please

---------- Post updated at 05:03 AM ---------- Previous update was at 02:43 AM ----------

I have a fixed with file with header & trailer length having the same length of the detail record file.

The details record length of this file is 24, for Header and Trailer the records will be padded with spaces to match the record length of the file
Currently I am adding 3 spaces in header and 6 spaces in trailer to match with detail record length

current value of my header is

Code:

Column Name  Data length
----------   ----------
A        1
B        2
C        2
D        8
E        8

current value of my trailer is

Code:

Column Name  Data length
----------   ----------
A        1
B        2
C        15

My requirement is to change the value of the second column(Column B) from xx to yyy both in header and trailer.
After this change I should have only two spaces in header and 5 spaces in trailer

I don't fully understand.
If you need a fixed record size, use printf:

Code:

awk '(NR<=2) {printf "%-24s\n",$0; next} ($1=="B") {printf "%-13s%-11s\n",$1,$2}' file

To change a certain value on the fly, you can use

Code:

{
awk '(NR<=2) {printf "%-24s\n",$0; next} ($1=="B") {$2="yyy"} {printf "%-13s%-11s\n",$1,$2}' header
cat detail
awk '(NR<=2) {printf "%-24s\n",$0; next} ($1=="B") {$2="yyy"} {printf "%-13s%-11s\n",$1,$2}' trailer
} > newfile

Thanks for the reply.
Let me explain the requirement again

I have a file with header and trailer which is fixed width
Header is having five columns & trailer is having 3 columns.The respective length of each column I have mentioned below.

Code:

Column Name  Data length
----------   ----------
A        1
B        2
C        2
D        8
E        8

current value of my trailer is 

Column Name  Data length
----------   ----------
A        1
B        2
C        15

sample records for header :-

Code:

1cc  12345   43434

I need to replace the above sample record second column value with yyy.i.e from cc to yyy.

Code:

1yyy  12345  43434

So you need to split the data into 3 (x , xx and xxxxxxxxxxxxxxx) overwriting the second potion with "yyy" ?

Code:

perl -ne 'print substr($_ ,0,1),"yyy",subsr($_,3)' file_name

---------- Post updated at 02:53 PM ---------- Previous update was at 02:53 PM ----------

So you need to split the data into 3 (x , xx and xxxxxxxxxxxxxxx) overwriting the second potion with "yy" ?

Code:

perl -ne 'print substr($_ ,0,1),"yy",subsr($_,3)' file_name

Thank you..

I tried but its not working..Mine is a unix machine, In which pearl command is not working

This replaces position 2-3 with yyy, shifting the remainder by +1

Code:

sed 's/\(.\{1\}\)../\1yyy/'

Thanks a lot.Its working fine.

if possible can you please tell me how to replace only the header & trailer of the file rest of the records need to be the same

---------- Post updated 08-03-13 at 12:48 AM ---------- Previous update was 08-02-13 at 07:17 PM ----------

Code:

sed 's/\(.\{1\}\)../\1yyy/'

This command is actually replacing the value of all the records in the file.But I need to replace the value of header & trailer only .Please some one help here