Copy a column to another column in UNIX fixedwidth file

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http://www.unix.com – Hi All, I have a fixedwidth file of length 3000. Now i want to copy a column of 4 chars i.e( length 1678-1681) to column 1127 – 1171 to the same file. Please let me know how can i achive using a single command in fixed width file. Also source column length is 4 chars and target column length is 45 chars. So while coying the column the value should be left adjusted to the column. thanks, Kiran (HowTos)