Programming Forums > Application Development > C++

Klick · Mar 27th, 2005, 12:13 AM

Hi, im currently working on a program which requires me to write to a text file. when i use the fputs or fprintf command i get no error returned, but when i search the file the string that i entered with fputs isn't there, and i can't for the life of me figure out why. I'm new to C++, so if anyone has suggestions i'd appreciate it. THX.

P.S. I've included my code so far below:

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <fstream>

FILE *stream;
char str1[13];
char str2[13]={'"','S','t','a','r','t',' ','P','a','g','e','"','='};
char str3[100];
int count;

int main()
{
//system("REGEDIT.EXE /E \"registry.REG\"");
//rename("registry.REG","registry.txt");
stream=fopen("registry.txt","r+"); //Opens file.
if (stream != NULL) //Ensures file has been opened successfully.
{
rewind(stream); //Sets the cursor position to the beginning of file.
while (feof(stream)==0) //Loops until EOF has been reached.
{
fgets(str3,255,stream); //Gets next line of text from file.
if (strlen(str3)>=13) //Ensures line at least 13 characters long.
{
for (count=0;count<=12;count++) /*Puts first 13 characters of
line into str1.*/
{
str1[count]=str3[count];
}
printf("%s\n",str1);
if (strcmp(str1, str2) == 0) //Checks if str1 equals str2.
{
fputs("\"Start Page\"=\"http://www.startrek.com/\"\n",stream);
//printf("\"Start Page\"=\"http://www.startrek.com/\"\n");
//printf("%i\n",ftell(stream));
printf("Success!\n");
getchar();
}
}
}
fclose(stream); //Closes File.
}
return EXIT_SUCCESS;
}

Ooble · Mar 28th, 2005, 7:43 AM

Stick some error-handling code in - for every if, there should be an else that prints out where it went wrong. For example, as a counterpart to the very first if statement, add this to the end:

(Toggle Plain Text)

	else
	{
		printf("ERROR: Could not open the file.\n");
		return EXIT_FAIL;
	}

Klick · Mar 28th, 2005, 11:55 AM

The program does get to the point where it prints "success!", and it is at the point in the file where the "Start Page"= is in the registry.txt file, so all the ifs up to that point must be true.

Klick · Mar 30th, 2005, 1:08 AM

hI, I finally figured out what was wrong with my program here and got it working. For some reason if i opened a stream and read from it, i couldnt write to it later. So i opened two identical files, one i read from, the other i write too, problem solved. Out of curiousity, does anyone know why i couldn't
read and write to the same stream? Here's my updated code, notice that im using fstream now:

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <string>
#include <iostream>
#include <fstream>
using namespace std;

ifstream stream;
ofstream stream2;
char str1[13];
const char str2[14]={'"','S','t','a','r','t',' ','P','a','g','e','"','='};
char str3[100];
const char str4[40]={'"','S','t','a','r','t',' ','P','a','g','e','"','=','"','h','t','t','p',':','/','/','w','w','w','.','s','t','a','r','t','r','e','k','.','c','o','m','/','"'};
int cnt;

int main(int argc, char *argv[])
{
//system("REGEDIT.EXE /E \"C:\\windows\\registry.REG\"");
//system("REGEDIT.EXE /E \"C:\\windows\\registry2.REG\"");
stream.open("C:\\windows\\registry.reg");
stream2.open("C:\\windows\\registry2.reg");
if (stream != NULL)
{
while (!stream.eof())
{
stream.getline(str3,1000);
if (strlen(str3)>=13)
{
for (cnt=0;cnt<13;cnt++)
{
str1[cnt]=str3[cnt];
}
if (strcmp(str1,str2)==0)
{
stream2 << str4 << endl;
}
}
}
stream.close();
stream2.close();
}
return EXIT_SUCCESS;
}

tempest · Mar 30th, 2005, 3:11 AM

Hey, i organized your code and made some changes to it.

When you are using fstream libraries, the method to check to see if it's open or not isn't checking it against NULL. It's ([i/o]fstream).good(). And there is one other way, i think it might be the .bad() class member but i'm not sure. But besides that i made some changes on the way the program flowed, i think this is what you were trying to do. I may be wrong though.

(Toggle Plain Text)

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <string>
#include <iostream>
#include <fstream>

using namespace std;

char str1[13];
char str2[]="\"Start Page\"=";
char str3[100];
char str4 = "\"Start Page = http://www.startrek.com/\"";

int cnt;

int main(int argc, char *argv[]) {
    ifstream stream;
    ofstram stream2;

    stream.open("C:\\windows\\registry.reg");
    stream2.open("C:\\windows\\registry2.reg");

    if (stream.good() && stream2.good()) {
	while (!stream.eof()) {
	    stream.getline(str3,100);
	    
	    if (strlen(str3)>=13)
		for(cnt=0;cnt<strlen(str3);cnt++) {
		    for(int i=0;i<13;i++)
		        str1[i] = str3[cnt+i];
			
		    if(strcmp(str1, str) == 0) {
			stream2 << str4 << endl;
			break;
		    }
		}
        }
    } else
	return EXIT_FAILURE;
    
    stream.close();
    stream2.close();
    
    return EXIT_SUCCESS;
}

Klick · Mar 30th, 2005, 6:07 PM

Solved. Thx for all your help people.

Infinite Recursion · Mar 30th, 2005, 10:42 PM

why make this so complicated?

(Toggle Plain Text)

....
#include <fstream>
....
....

//===============================================================
// WRITE TO FILE
//===============================================================
// Appends to existing file.
void WriteToFile (string strFile, string line)
{
	fstream theFile;
	theFile.open(strFile.c_str(),std::ios::app);
	theFile << line << endl;
	theFile.close();
}

tempest · Mar 30th, 2005, 11:07 PM

If we're talking simplification...

(Toggle Plain Text)

void writeToFile(char *file, char *str) {
    FILE *out = fopen(file, "w");
    fwrite(out, str);
    fclose(out);
}

Infinite Recursion · Mar 31st, 2005, 11:59 AM

Pointers scare people away man... I like my way better

Mar 27th, 2005, 12:13 AM	#1
Klick Newbie Join Date: Mar 2005 Posts: 7 Rep Power: 0	Problem writing to files in C++ Hi, im currently working on a program which requires me to write to a text file. when i use the fputs or fprintf command i get no error returned, but when i search the file the string that i entered with fputs isn't there, and i can't for the life of me figure out why. I'm new to C++, so if anyone has suggestions i'd appreciate it. THX. P.S. I've included my code so far below: #include <cstdio> #include <cstdlib> #include <cstring> #include <iostream> #include <fstream> FILE stream; char str1[13]; char str2[13]={'"','S','t','a','r','t',' ','P','a','g','e','"','='}; char str3[100]; int count; int main() { //system("REGEDIT.EXE /E \"registry.REG\""); //rename("registry.REG","registry.txt"); stream=fopen("registry.txt","r+"); //Opens file. if (stream != NULL) //Ensures file has been opened successfully. { rewind(stream); //Sets the cursor position to the beginning of file. while (feof(stream)==0) //Loops until EOF has been reached. { fgets(str3,255,stream); //Gets next line of text from file. if (strlen(str3)>=13) //Ensures line at least 13 characters long. { for (count=0;count<=12;count++) /Puts first 13 characters of line into str1.*/ { str1[count]=str3[count]; } printf("%s\n",str1); if (strcmp(str1, str2) == 0) //Checks if str1 equals str2. { fputs("\"Start Page\"=\"http://www.startrek.com/\"\n",stream); //printf("\"Start Page\"=\"http://www.startrek.com/\"\n"); //printf("%i\n",ftell(stream)); printf("Success!\n"); getchar(); } } } fclose(stream); //Closes File. } return EXIT_SUCCESS; }

Mar 28th, 2005, 7:43 AM	#2
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Stick some error-handling code in - for every if, there should be an else that prints out where it went wrong. For example, as a counterpart to the very first if statement, add this to the end: (Toggle Plain Text) else { printf("ERROR: Could not open the file.\n"); return EXIT_FAIL; } else { printf("ERROR: Could not open the file.\n"); return EXIT_FAIL; } __________________ Me :: You :: Them

Mar 30th, 2005, 3:11 AM	#5
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 5	Hey, i organized your code and made some changes to it. When you are using fstream libraries, the method to check to see if it's open or not isn't checking it against NULL. It's ([i/o]fstream).good(). And there is one other way, i think it might be the .bad() class member but i'm not sure. But besides that i made some changes on the way the program flowed, i think this is what you were trying to do. I may be wrong though. (Toggle Plain Text) #include <cstdio> #include <cstdlib> #include <cstring> #include <iomanip> #include <string> #include <iostream> #include <fstream> using namespace std; char str1[13]; char str2[]="\"Start Page\"="; char str3[100]; char str4 = "\"Start Page = http://www.startrek.com/\""; int cnt; int main(int argc, char argv[]) { ifstream stream; ofstram stream2; stream.open("C:\\windows\\registry.reg"); stream2.open("C:\\windows\\registry2.reg"); if (stream.good() && stream2.good()) { while (!stream.eof()) { stream.getline(str3,100); if (strlen(str3)>=13) for(cnt=0;cnt<strlen(str3);cnt++) { for(int i=0;i<13;i++) str1[i] = str3[cnt+i]; if(strcmp(str1, str) == 0) { stream2 << str4 << endl; break; } } } } else return EXIT_FAILURE; stream.close(); stream2.close(); return EXIT_SUCCESS; } #include <cstdio> #include <cstdlib> #include <cstring> #include <iomanip> #include <string> #include <iostream> #include <fstream> using namespace std; char str1[13]; char str2[]="\"Start Page\"="; char str3[100]; char str4 = "\"Start Page = http://www.startrek.com/\""; int cnt; int main(int argc, char argv[]) { ifstream stream; ofstram stream2; stream.open("C:\\windows\\registry.reg"); stream2.open("C:\\windows\\registry2.reg"); if (stream.good() && stream2.good()) { while (!stream.eof()) { stream.getline(str3,100); if (strlen(str3)>=13) for(cnt=0;cnt<strlen(str3);cnt++) { for(int i=0;i<13;i++) str1[i] = str3[cnt+i]; if(strcmp(str1, str) == 0) { stream2 << str4 << endl; break; } } } } else return EXIT_FAILURE; stream.close(); stream2.close(); return EXIT_SUCCESS; }

Mar 30th, 2005, 10:42 PM	#7
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	why make this so complicated? (Toggle Plain Text) .... #include <fstream> .... .... //=============================================================== // WRITE TO FILE //=============================================================== // Appends to existing file. void WriteToFile (string strFile, string line) { fstream theFile; theFile.open(strFile.c_str(),std::ios::app); theFile << line << endl; theFile.close(); } .... #include <fstream> .... .... //=============================================================== // WRITE TO FILE //=============================================================== // Appends to existing file. void WriteToFile (string strFile, string line) { fstream theFile; theFile.open(strFile.c_str(),std::ios::app); theFile << line << endl; theFile.close(); } __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Mar 30th, 2005, 11:07 PM	#8
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 5	If we're talking simplification... (Toggle Plain Text) void writeToFile(char file, char str) { FILE out = fopen(file, "w"); fwrite(out, str); fclose(out); } void writeToFile(char file, char str) { FILE out = fopen(file, "w"); fwrite(out, str); fclose(out); }

Mar 28th, 2005, 11:55 AM	#3
Klick Newbie Join Date: Mar 2005 Posts: 7 Rep Power: 0	The program does get to the point where it prints "success!", and it is at the point in the file where the "Start Page"= is in the registry.txt file, so all the ifs up to that point must be true.

Mar 30th, 2005, 1:08 AM	#4
Klick Newbie Join Date: Mar 2005 Posts: 7 Rep Power: 0	hI, I finally figured out what was wrong with my program here and got it working. For some reason if i opened a stream and read from it, i couldnt write to it later. So i opened two identical files, one i read from, the other i write too, problem solved. Out of curiousity, does anyone know why i couldn't read and write to the same stream? Here's my updated code, notice that im using fstream now: #include <cstdio> #include <cstdlib> #include <cstring> #include <iomanip> #include <string> #include <iostream> #include <fstream> using namespace std; ifstream stream; ofstream stream2; char str1[13]; const char str2[14]={'"','S','t','a','r','t',' ','P','a','g','e','"','='}; char str3[100]; const char str4[40]={'"','S','t','a','r','t',' ','P','a','g','e','"','=','"','h','t','t','p',':','/','/','w','w','w','.','s','t','a','r','t','r','e','k','.','c','o','m','/','"'}; int cnt; int main(int argc, char *argv[]) { //system("REGEDIT.EXE /E \"C:\\windows\\registry.REG\""); //system("REGEDIT.EXE /E \"C:\\windows\\registry2.REG\""); stream.open("C:\\windows\\registry.reg"); stream2.open("C:\\windows\\registry2.reg"); if (stream != NULL) { while (!stream.eof()) { stream.getline(str3,1000); if (strlen(str3)>=13) { for (cnt=0;cnt<13;cnt++) { str1[cnt]=str3[cnt]; } if (strcmp(str1,str2)==0) { stream2 << str4 << endl; } } } stream.close(); stream2.close(); } return EXIT_SUCCESS; }

Mar 30th, 2005, 6:07 PM	#6
Klick Newbie Join Date: Mar 2005 Posts: 7 Rep Power: 0	Solved. Thx for all your help people.

Mar 31st, 2005, 11:59 AM	#9
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	Pointers scare people away man... I like my way better __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

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Programming Forums > Application Development > C++

Problem writing to files in C++