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replace characters in a file

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# 1  
Old 10-22-2008
replace characters in a file
Hi,

I have a file in which i want to replace the charaters from position 3-5 with a particular string for the first line.

For ex

The file contains

abcdefghij
jkdsflsfkdk
908090900

i want to replace the characters 3-5 for the first line as 678

so, the file should look like

ab678fghij
jkdsflsfkdk
908090900

i am editing it in vi and doing the change. But we have so many file to do the same thing, and i am trying to automate it. can someone help.
# 2  
Old 10-22-2008
One way:

Code:
awk -v var="678" 'NR==1{print substr($0,1,2) var substr($0,6);next}1' file > newfile

Regards
# 3  
Old 10-22-2008
wher are we specifying the character numbers as 3-5
# 4  
Old 10-22-2008
Code:
sed '1s/\(..\)\(...\)\(.*\)/\1678\3/' file

# 5  
Old 10-22-2008
Quote:
Originally Posted by dnat
wher are we specifying the character numbers as 3-5
Nowhere, the command prints the first 2 characters of the first line, then the variable and at last position 6 until the end of the line.

Regards
# 6  
Old 10-23-2008
thank you..but can you tell me how i can mention the characters 3-5. i have just given examples here and my main data is something different.
# 7  
Old 10-23-2008
In a nutshell.

i want to cut the characters 3-5 from the file, change it and insert the changed value in the position 3-5.
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