easy way to modify textfile

[Gunnar G]

Hello.
If I wish to open a huge textfile and only change the 300th line in the
file, how do I do that?

 

[Maxim Yegorushkin]

If I wish to open a huge textfile and only change the 300th line in the
file, how do I do that?

Use a stream editor, such as sed.

 

[Gunnar G]

Use a stream editor, such as sed.
And if that is not an option?
I solved it by storing all the lines in a vector, then reopen the file in
non-appending mode and write all the lines.

There must be a better way...

 

[Maxim Yegorushkin]

And if that is not an option?
I solved it by storing all the lines in a vector, then reopen the file in
non-appending mode and write all the lines.

There must be a better way...

You could read the file by chunks in a buffer rather then reading the
whole in the vector. This way you avoid all the problems related to memory
allocation.

 

[Karl Heinz Buchegger]

Hello.
If I wish to open a huge textfile and only change the 300th line in the
file, how do I do that?

open input file
open a new file for output

counter = 0;

while( line can be read from input ) {
increment counter
if counter equals 300
write replacement line to output
else
write original line to output
}

close input file
close output file
delete input file
rename output file to the input file name

done

 

[Panjandrum]

And if that is not an option?
I solved it by storing all the lines in a vector, then reopen the file in
non-appending mode and write all the lines.

There must be a better way...

If the line isn't longer or shorter afterwards you can use random
access.