Shell Programming and Scripting

What's the difference between the 3 sections header,detail,trailer?
Could you give 3 example lines for each? (To find a contents criterion.)
Perhaps there are fixed line numbers, e.g. trailer starts at line 100 or is 10 lines long?

Please find the below record.In this the first and the last record is header & trailer.

Code:

HAR  1129201202:33:13   
D3065507                           
TAR000000000000144

Suppose the file name is Test123.txt if I use the command

sed 's/\(.\{1\}\)../\1yyy/' Test123.txt it will give me the result as mentioned below

Code:

Hyyy  1129201202:33:13   
Dyyy65507                          
Tyyy000000000000144

It should not be like above .It should change only for header & trailer and also it is adding one extra space at the end.I don't want that space

I have copied the CODE segments from your last post replacing each space character with a lowercase letter s as shown here:

Code:

HARss1129201202:33:13sss
D3065507sssssssssssssssssssssssssss
TAR000000000000144ssssss

and

Code:

Hyyyss1129201202:33:13sss
Dyyy65507ssssssssssssssssssssssssss
Tyyy000000000000144s

So, you will note that the output doesn't have an additional space character in the last line of your output; instead, it is missing five space characters. This change in the number of spaces at the end of the last line in your output was not caused by the sed command:

Code:

sed 's/\(.\{1\}\)../\1yyy/' Test123.txt

You must be doing something else that you haven't shown us that is making that change.

Its actually my mistake when I did a copy ..

I don't know how I can make my requirement understand

Code:

HAR  1129201202:33:13   
D3065507                
TAR000000000000144

In the above example which I show you , I need to replace AR with YYY.
The below code will replace for all the three records, but I need to replace only for the first and last record .And also while replacing, it shouldn't add an extra space.It should remove one space and add that record Means Length should be only 24.
Note: -Its a fixed width file.All the records will have a length of 24
sed 's/\(.\{1\}\)../\1yyy/'

I created a file with your posted data. Two things to note here:
(1) I replaced all spaces by "*" so they are easily visible.
(2) The length of each line is 24. It wasn't so in your post, but I think that was due to copy/paste issues.

Here's my file:

Code:

$ 
$ cat f01
HAR**1129201202:33:13***
D3065507****************
TAR000000000000144******
$ 
$ # check length of each line
$ awk '{print length}' f01
24
24
24
$ 
$

Now you mention two things in your post -

(a) you want to replace all "AR"s by "yyy"
(b) you want to replace only first and last record (the head and tail record)

So, will "AR" be present only in the first and last record i.e. only in the head and tail record? Let's say it does. Then we can use "AR" to match the lines we want to change:

Code:

$ 
$ 
$ sed '/^.AR/{s/AR/yyy/; s/.$//}' f01
Hyyy**1129201202:33:13**
D3065507****************
Tyyy000000000000144*****
$ 
$

Here, "/^.AR/" means - "find out all lines that have any character at the beginning, followed by AR". This will work only on the first and last line. The second line will remain as it is.

The first operation "s/AR/yyy/" performs the required substitution.

The second operation "s/.$//" removes the last character in the line so that the length is constant. Note that it removes the last character - which could be a space or something else.

Thanks for the reply
Actually I am getting below issue

Code:

sed: command garbled: /^.AR/{s/AR/yyy/; s/.$//}

Can you please look into this

A semi-colon is missing:

Code:

$ sed '/^.AR/{s/AR/yyy/; s/.$//;}' f01