how to add line at bottom of file in linux

dnyan · #1 (**permalink**) 04-20-07, 08:54

please tell me how to add line at bottom of file in linux by using a sed or awk ?
is a script for the same ?

stolze · #2 (**permalink**) 04-21-07, 04:39

Code:

echo "line" >> file

I'm sure awk can do that as well (for example in the END block), but why make it more complicated?

Tyveleyn · #3 (**permalink**) 04-21-07, 06:42

Hi,

I understood your question differently then Knut did and think something like this is what you're looking for.
Like Knut mentioned, here's an 'awk' example. The advantage is that first the complete file is read into memory and after that the memory content is written to the file on disk again (including the extra last line). With this you can overwrite the original file in one step because awk has finished reading the input filestream before the output filestream is created. (Offcourse this only works if there's enough memory available to store the complete file.)
Something that's going terribly wrong with 'sed', where you allways have to store the output in a helpfile first and overwrite the original with that.
Awk solution:

Code:

#!/bin/bash                             
                                        
awk '   {   line[NR] = $0   }           
    END {                               
            for(i = 1; i <= NR; i++)    
                print line[i] > FILENAME
            print "" > FILENAME         
        }' $1

Sed solution:

Code:

#!/bin/bash       
                  
sed '$s/$/\       
/' $1 > "${1}.tmp"
mv "${1}.tmp" $1

Regards

stolze · #4 (**permalink**) 04-21-07, 12:44

Yeah, it really depends on what you want to do. Reading the entire file into main memory just to add a line at the end and leaving the rest of the file untouched would be overkill and a huge waste of resources, of course. Even if you need to modify the file, I would still recommend to not rely on main-memory. Only for really small (just a few MB) files, this is acceptable.

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