Thread: Few Questions

How can I write to the beginning of the file? I have it working now but it overwrites in it's path which is annoying :P

Also is there anyway I can have it read a file and take out a certain line of code?

LAST BUT NOT LEAST how can I use variables in system()? Right now I have it retardidly writing the command to a file, reading the file to a var, then run the var, when I want it to be able to system("yada %s") type thing.

*Edit* One last thing, How can I make it read a sentence w/ spaces? I currently have it reading a char that works and stuff, but it stops at spaces, thanks again.

I'm still pretty new to C although I have all the basics down, any help would be appreciated ^_^ Thanks!

> How can I write to the beginning of the file?
You can't insert stuff into the middle of a file - you have to rewrite the whole file.

> Also is there anyway I can have it read a file and take out a certain line of code?
Use fgets() to read each line, and a counter to stop at the one you want.

If the file is fairly static (doesn't change), fairly large (several MB), and you need to do this a lot, then you can build an index. But that does require a lot of extra work at the start.

> how can I use variables in system()?
See other recent posts, it's being discussed right now in another thread.

Originally Posted by sand_man

a space can be read the exact same way as a character.
show us some code.

im not sure if this is what you meant,
to start a new file or to overwrite and old file you need to open it like this

Code:

fp = fopen("C:\path\","w");

to append to the end of the file you change the 'w' to 'a'

Code:

fp = fopen("C:\path\","a");

I meant how do you ADD lines of code to the beginning of a file that already contains information.

> How can I write to the beginning of the file?
You can't insert stuff into the middle of a file - you have to rewrite the whole file.

Damn.

> Also is there anyway I can have it read a file and take out a certain line of code?
Use fgets() to read each line, and a counter to stop at the one you want.

I'm still kinda new to C so I don't get the counter part o.o Throw a hint? XD

> how can I use variables in system()?
See other recent posts, it's being discussed right now in another thread.

Thanks gonna look now

Originally Posted by Ne0

I meant how do you ADD lines of code to the beginning of a file that already contains information...

a. open file.
b. read old data to memory.
c. seek begin of file.
d. write new data begin of file
e. append data from memory to this file.
f. close file.