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Old 07-21-2011, 12:49 PM   #1
DBabo
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compare 2 text files and change lines


hello,
quick question:
in the shell. how do i compare 2 text files and change matching lines in one of the files ?

example:
cat file_1.txt
line_1
line_10
<eof>

cat file_2.txt
line_1
line_2
...
line_10
...
line_1000
<eof>
the result is file_3.txt
cat file3_txt:
# line_1
line_2
...
#line_10
...
line_1000
<eof>

Thank you.
Andrew
 
Old 07-21-2011, 01:05 PM   #2
rch
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man diff
 
Old 07-21-2011, 01:13 PM   #3
DBabo
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Quote:
Originally Posted by rch View Post
man diff
isn't it give you only those that are _not_ matching ?
 
Old 07-21-2011, 01:19 PM   #4
DBabo
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ok, an "ugly" approach:
take the file_1 and make it into file with sed's expressions. then feed to sed ....
 
Old 07-21-2011, 07:01 PM   #5
chrism01
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Actually, there's a whole load of diff type cmds http://linux.die.net/man/1/diff (see bottom of page).
I think you can get almost anything ie common and/or differences.
See also http://linux.die.net/man/1/comm
 
Old 07-22-2011, 12:11 PM   #6
DBabo
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Quote:
Originally Posted by chrism01 View Post
Actually, there's a whole load of diff type cmds http://linux.die.net/man/1/diff (see bottom of page).
I think you can get almost anything ie common and/or differences.
See also http://linux.die.net/man/1/comm
Chrism,
that's what i was thinking initially - get the common lines, feed them to sed and call it a day.

But then i started thinking - isn't it too much of file reading for such a simple operation - read 2 files to get common. Store in a third file. Read two files again to find matching lines and store the output to the final one.
There got to be a utility that does just this one step. So for now i settle with "ugly" approach, but i'm still left wondering...
 
Old 07-26-2011, 01:20 PM   #7
DBabo
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aha! and i just came across the (almost complete) solution http://www.linuxquestions.org/questi...2/#post4425011
 
  


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