UNIX for Dummies Questions & Answers

Well, just some questions then:

Why would you need to make the header and trailer ONLY 106 characters in length?

Usually, this is because an old mainframe type program is reading the file with a fixed record size. For fun, just check the size of your "D" records and see if they aren't 106 characters wide.

At any rate, here's a ksh solution:

Code:

cat file_in |
while read line; do
  case $line in
    [HT]*) printf "%s%-100.100s\n" $line " " ;;
        *) print $line ;;
  esac
done

Here's an awk solution:

Code:

 
cat file_in |
awk '
  /^H/ { printf( "%s%-100.100s\n", $0, " " ); next; }
  /^T/ { printf( "%s%-100.100s\n", $0, " " ); next; }
  { print; }
  '

Notice the use of the printf() in both solutions.

I also like this syntax for printf:

Code:

printf( "%-*.*s\n", 106, 106, string );

... where you can pass the width in as an argument to printf.
It's a smidge easier to modify later on...

The use of cat with awk and in a while loop is redundant.

Code:

awk '
}
  ...
}
' file_in

Code:

while read line; do
 ..
done < file_in

Regards

True.

However, I find that seeing the name of the file at the beginning
of a pipe-line, in general, is convenient for legibility and comprehension.
That is, no searching to the end of a lenghthy pipe or awk script to see what the input file is.

Right, but it's not a bad habit to make known how to avoid cat to make the code more efficient (and faster).

Regards