Læse og skrive til filer

prøv dette

#include <iostream.h>
#include <fstream.h>
#include <conio.h>
#include <string.h>

int main(){
  FILE* fp;
string row;
string nyRow;

  fp = fopen("test.txt","r");
  while(row=fgets(fp,1024)){
    nyRow=nyRow+row;
}
fclose(fp);

cout<<nyrow<<endl;

return 0;
}

Du specificerer ikke hvor filen ligger på disken, er du sikker på den ligger i "current directory"?

Ellers kan du prøve at skrive hele stien, fx:

"C:\\test.txt" (husk dobbelt backslash)

Ja, den ligger i samme biblotek som cpp-filen.

Men jeg får stadig fejl, hvis jeg prøver at compile den.

c:\cpp\filer.cpp 12:cannot convert 'FILE *' to 'char *' in function main()
c:\cpp\filer.cpp 12: Type mismatch in parameter '__s' (wanted 'char*', got 'FILE *') in function main()
c:\cpp\filer.cpp 12:Too few parameters in call to 'fgets(char *,int,FILE *)' in funktion main()
c:\cpp\filer.cpp 12:Illegal structure operation in function main()
c:\cpp\filer.cpp 17:Undefined symbol 'nyrow' in function main()

Du bruger jo forkerte argumenter i funktionen fgets...

#include <iostream.h>
#include <stdio.h>
#include <string>
using std::string;

int main()
{
    char row[1024];
    FILE* fp;
    fp = fopen("test.txt","r");
    while(fgets(row, 1024, fp))
    {
        cout << row << endl;
    }
    fclose(fp);
    return 0;
}

jpk>>Mumsk, skønt, dejligt, perfekt... det virker for mig

så skal jeg bare have fundet ud af hvordan jeg skrive ind til en fil :o)

Du bruger igen fopen til at åbne/oprette en fil.
I ovenstående bruger du "r", her kan du se hvilke muligheder der er...
Fra MSDN:

"r"

Opens for reading. If the file does not exist or cannot be found, the fopen call fails.

"w"

Opens an empty file for writing. If the given file exists, its contents are destroyed.

"a"

Opens for writing at the end of the file (appending) without removing the EOF marker before writing new data to the file; creates the file first if it doesn’t exist.

"r+"

Opens for both reading and writing. (The file must exist.)

"w+"

Opens an empty file for both reading and writing. If the given file exists, its contents are destroyed.

"a+"

Opens for reading and appending; the appending operation includes the removal of the EOF marker before new data is written to the file and the EOF marker is restored after writing is complete; creates the file first if it doesn’t exist.

Du kan så bruge fputs (modsætningen til fgets), til at skrive til filen...

Det vil sige at det er ligesom når man åbner en fil med php, og at hvis jeg skal skrive til filen er det sådan:
#include <fstream.h>

int main(){
char row;
FILE* fp;
fp = fopen("test.txt","a");
char = "Dette er en test";
fputs(fp,char);
fclose(fp)
return 0;
}

Tjo, noget lign., men du laver et par fejl:

Prøv istedet dette:

char newRow[] = "Dette er en test";
fp = fopen("test.txt","a");
fputs(newRow, fp);
fclose(fp);

Ellers er der jo de udmærkede funktioner i Windows:

#include <string>
#include <windows.h>

void main() {

  string tekst = "Dette vil jeg skrive til filen";
  HANDLE hFile;
  hFile = CreateFile("c:\\minfil.txt", GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);

  if(hFile != INVALID_HANDLE_VALUE) {
      if(tekst.length() > 0) {
      DWORD dwWritten;
        if( WriteFile(hFile, tekst.c_str(), tekst.length(), &dwWritten, NULL) == 0 )
          cerr << "Error writing file" << endl;
      }
      CloseHandle(hFile);
  }

  HANDLE hFile2;
  OFSTRUCT openfile;
  (HFILE*)hFile2 = OpenFile("c:\\minfil.txt", &openfile, OF_READ);
 
  char buffer[10];
  DWORD numbytesToRead = 5;
  DWORD numbytesRead;
  DWORD result;
 
  if( hFile2 != INVALID_HANDLE_VALUE) {
      while( true ) {
        result = ReadFile( hFile2, &buffer, numbytesToRead, &numbytesRead, NULL );
        if (result &&  numbytesRead == 0 )
            break;
        cout << buffer;
      }
      cout << endl;
  }
  system("pause");
}

glemte lige CloseHandle(hFile2); lige før system("pause");

Jeg skulle bare bruge en enkelt forstålig løsning, ellers tak