shivaki
asked on
How to delete a Line or word in file that is opened by File pointer in C
When ever I am opening any existing file by using File* pointers in C. I am facing the problem of inserting some new strings/Lines(other than at the end of file) OR deleting some strings/Lines. To do this I am using explicitly some temporary buffers. Is there any simple way to do this. Or any standard API is available to do this. Please answer me.
ASKER CERTIFIED SOLUTION
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
No there is no magic way to do this
You can eiher do as you do, or alternatively you can open files for read/write. This way you can read part of the file and write to other parts. Obviously if you are inserting you need to read any stuff you want to keep before overwritting it.
The way round this is to use a file structure with indexes (e.g. ISAM or a database engine, etc.) so you can do inserts without reading the file into memory first.
You can eiher do as you do, or alternatively you can open files for read/write. This way you can read part of the file and write to other parts. Obviously if you are inserting you need to read any stuff you want to keep before overwritting it.
The way round this is to use a file structure with indexes (e.g. ISAM or a database engine, etc.) so you can do inserts without reading the file into memory first.
ASKER
ThanQ but Let me to make it more specific. If Iam inserting a new string or deleting I have to protect the previous contents. this I can achieve by using the buffers. What the actual problem of mine is to include these buffers into the actual file I have to delete the exising file and create a new file with the same name and I can do that. By this there is a potential danger that I have pay the cost of file attributes ,i.e file creation date, acutal owner of that file ... To protect all of these I have to explicitly save the file attributes. I am seeking for a simple solution for this with in 'C' environment.
ASKER
This is fine for insertion since the overwritten buffer had more length than existing one. What about if I want to delete some of the file contents?
you can read the while file and copy to a temporary. When you get to lines/words that you don't want - then don't copy. When you get to where you want new lines/words - then write them out.
When finished rename files or re-open the old input file for output and the output file for input and copy everything back again.
Alternatively, read the whole file into structures/arrays in memory, modify it there and write it all back out again.
When finished rename files or re-open the old input file for output and the output file for input and copy everything back again.
Alternatively, read the whole file into structures/arrays in memory, modify it there and write it all back out again.
ASKER