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How to replace the last pattern using sed?

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# 1  
Old 03-29-2011
How to replace the last pattern using sed?
myfile:

AAAaaa
BBBbbb
CCCccc
AAAeee
DDDddd

how to replace the last AAA as EEEEE using sed?

like this:

AAAaaa
BBBbbb
CCCccc
EEEEEeee
DDDddd
# 2  
Old 03-29-2011
Perhaps this post will provide some insight
Take a look at:

https://www.unix.com/shell-programmin...rence-sed.html
# 3  
Old 03-29-2011
Code:
sed '/eee/s/AAA/EEEEE/' infile

---------- Post updated at 03:44 PM ---------- Previous update was at 03:42 PM ----------

Code:
# cat tst
AAAaaa
BBBbbb
CCCccc
AAAeee
DDDddd

Code:
# sed '/eee/s/AAA/EEEEE/' tst
AAAaaa
BBBbbb
CCCccc
EEEEEeee
DDDddd

# 4  
Old 03-29-2011
don't use the eee after AAA，because it may not be eee.
# 5  
Old 03-29-2011
So we miss some criteria to answer your question : give more clue

You want to replace which AAA ?

all but not the one in the first line ?

Only the last occurrence of AAA found ?

Only the second occurrence of AAA found ?

other ?
# 6  
Old 03-29-2011
Unless this is to be part of a pipeline, why sed? Using sed, you'd have to store each occurrence of "AAA" and all subsequent lines until the next occurrence of "AAA" exclusive or the final line of the file, print the block if the end of file has not been reached or perform the substitution if it has.

On the other hand, this is a trivial matter using ed. Set the current line to the first line, search backwards for the first occurrence of "AAA", and then perform the substitution.

Regards,
Alister
# 7  
Old 03-29-2011
I wanna replace ONLY the last occurrence of AAA using one shell command such as sed or awk.
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