using the seekg command for files

[Guest_imported]

Hi, I currently need help on the seekg command. The problem is that I do not know how to write information to a file in the same block size (I am using random access)
for example:
I want to search the 9th and 17th object in a file:
---------------------------------------------------
A
B
C
D
...
X
Y
Z
---------------------------------------------------
the 9th and 17th should be I and Q
I used the command fin.seekg(9, ios::beg);
there wasn't any errors but it outputted D instead...
the object of my program is to find the I and Q and replace them to X. If anyone of you need to look at the source code i will post it here again... thank you.

 

[ankan]

Keep these in mind...
1) The argument in seekg is the absolute position in the file (in bytes). This includes white spaces and all.
2) The bytes in a file are numbered starting with 0.

So to get to the 'n'th object in a file in which the field width of each object is 'w'...
fin.seekg( w*(n-1), ios::beg)
...is what needs to be done. This is for reading. For writing you need to use seekp. Ankan.

Please do correct me if I am wrong. s-)

 

[Pavlo]

Greetinx!

If your file is shown as previous example, you should take into account a line feed and carriage return symbols, which are place after of each letter. Happy programming!))