how to copy contents in one file in to another file?

Question

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i want to copy contents in one file in to another file.

C

fPout=fopen("parse.txt","r")
fPin=fopen("dpl.txt","w")
 
 do
 {
       a = fgetc(fPout);
      fputc(a,fPin);
 }
    while(a!=EOF);

i'm using this method but it shows error while compiling like multiple declaration,type mismatch etc. Also i've tried fread function but it doesn't work please help.....

Posted 9-Jun-15 21:10pm

Superdude Rahul

Updated 9-Jun-15 22:53pm

v3

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3 solutions

Solution 1

Look at your variable names, you use fPout for the input file, and fPin for the output file. You then try to read from a non-existent file referred to as fPParse. You also say i've tried fread function but it doesn't work, which tells us nothing; and having used fread extensively myself, I know that it does work.

Posted 9-Jun-15 21:22pm

Richard MacCutchan

Solution 2

Don't do it; it could be prohibitively slow on some bigger file. Read and write bytes by big chunks:
http://www.techonthenet.com/c_language/standard_library_functions/stdio_h/fread.php[^],
http://www.techonthenet.com/c_language/standard_library_functions/stdio_h/fwrite.php[^].

Be careful to check up the return value of fread. It tells you the number of actually read bytes. As soon as your number of actually read bytes is less than the requested block size, it indicates that this is the last block. This way, you don't even need a check for end of file.

How big should be the block? It depends. On modern PC systems, it could be a megabyte, several megabytes, something like that.

—SA

Posted 9-Jun-15 21:29pm

Sergey Alexandrovich Kryukov

v2

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CPallini · Accepted Answer · 2015-06-09T21:39:00

I would use a ssytem facility for just copying files (e.g. system("cp filein fileout"); on linux). Anyway the correct code to accomplish that should be

C#

#include <stdio.h>

int main()
{
  FILE * fpin, *fpout;

  int i;

  fpin = fopen("parse.txt", "r");
  if ( !fpin )
  {
    // handle error here
  }
  fpout = fopen("dpl.txt", "w");
  if (!fpout)
  {
    // handle error here
  }

  while ( (i = fgetc(fpin) ) != EOF )
  {
    fputc(i, fpout);
  }

  fclose(fpout);
  fclose(fpin);

  return 0;
}

Please note that errors on fopen must be properly handled (e.g. in all but trivial test programs, the acquired resources must be released).