Programming

Hi All,

Its been a long time since i did any programming and I am trying to get back into it as part of also learning Linux. Coming from a Cpp background i am trying to write some simple code just using C.

I want to create a simple log file but instead of appending to the end of the file i want to prepend it at the start. Try as i might i cant find any references to prepending text to a file.

I have tried rewind and fprintf to get to the top of the file but it overwrites existing entries at the top. How can i insert the text. Secondly I have read it is better for portability to use the Low Level I/O functions like open() read(), write and creat(). Can some one give me an example using the buffered methods like fopen, fprintf streams and the unbuffered methods like open() write() etc. I have read that fopen actually calls open() to open the file but provides a buffered stream.

I would appreciate your help very much. The books i have dont seem to go into much detail and though I have found many examples of reading and writing they dont seem to cover how to prepend. I suppose i could create a new file, but this seems to be a long way around the problem.

Thanks in advance and Regards

There are a lot of ways. Here is one.

1 open a temp file. Write the new lines to it.
2. open the log file - read the lines from the log ; write them to the temp file
3. close both files
4 rename the temp file as the logfile.

Jim,

Thanks, I had considered that but it seems to me a round about way. I was hopping for a more direct approach.

Regards
Netwolf

Another possibility:

1 read the contents of the file in a buffer
2 write the new lines to the file
3 write the buffer to the file

Regards