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basic file functions

Posted on 1998-07-30
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Last Modified: 2010-04-02
Hi,
How can I:
1. delete file from a directory (I am not in this directory)?
2. edit a file , also, i am not in this file directory?
3. search a string in a file?
4. errors in finding file.

Thanks A lot,
Tomer Leicht
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Question by:tomerl
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nietod earned 200 total points
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answers coming.
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by:nietod
ID: 1169035
I assume we are talking standard C++ right?  you don't want to be using a specific OS's procedures, like the Windows API?

1. to delete a file use remove() from stdio.h or io.h.  You specify a string that is the path and file name of the file to be removed.

2.  editing a file can mean anything.  (editing a text file is very different than editing a database file)  I assume you mean you want to modify a file in some way.  I'll explain how to modify it in general, you will have to decide ont he specifics for you case.

  you open the file with fopen(), read data from it with fread(), write new data to it with fwrite(), seek to different positions for reading/writting with fseek() and close the file with fclose().  read about these and ask if you have questions.
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by:nietod
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3. you open the file and read it in memory then search for the string using strstr().  If the file is too large to read into memory at one time, you can read it in pieces and search each piece.  The danger is if the string starts at the end of one piece and ends at the start of another you won't find it.  There are ways around this.  The easiast (not the most efficeint) is to copy the last (n-1) bytes from the end of the buffer (piece) to the the start where n is the length of the string you are looking for.  Then read in the new piece after those n-1 bytes.
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by:nietod
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>> 4. errors in finding file.
what do you mean by this?
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