Thread: Help with file read/write

Hi, i'm learning basic file read/write methods and i'm having trouble with this simple program.
It compiles without error but the text file does not show up on my desktop.
I've tried replacing "~" with "file://" and i am still not getting any results
I'm using gcc in Terminal(Mac)

Code:

#include <stdio.h>

int main() {
	FILE *handle;
	handle = fopen("~/Users/Jem/Desktop/test.txt","w");
	
	if (handle==NULL) {
		printf("Error opening file\n");
	}else {
		fprintf(handle,"TESTING");
		fclose(handle);
	}
	return 0;
}

thanks!
Also. how can i read the contents of the file? I tried the code below but i got this error:
"c:10: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘struct FILE *’ "
so i tried casting with "(char*)" in front of "handle" in the printf(); that time it compiled but nothing was printed. Help appreciated.

Code:

#include <stdio.h>

int main() {
	FILE *handle;
	handle = fopen("/Users/Jem/Desktop/test.txt","r");
	
	if (handle==NULL) {
		printf("Error opening file\n");
	}else {
		printf("%s",handle);
		fclose(handle);
	}
	return 0;
}

Or even better, recognize what ~ means: ~ means your own personal home directory. So perhaps you want "~/Desktop/test.txt" instead.

Originally Posted by Dino

~ is understood in the shell, but not in fopen.

Oh well spotted. Sorry.

ok, i used fscanf() instead and got some unexpected results. The test.txt file says "TESTING... TESTING"
when i run the program, i get the output:

Code:

TESTING?

here's the whole thing:

Code:

#include <stdio.h>

int main() {
	char message[50];
	FILE *handle;
	handle = fopen("/Users/Jem/Desktop/test.txt","r");
	
	if (handle==NULL) {
		printf("Error opening file\n");
	}else {
		fscanf(handle,"%s",message);
		fclose(handle);
		printf("%s\n",message);
	}
	return 0;
}

Originally Posted by bluej322

ok, i used fscanf() instead and got some unexpected results. The test.txt file says "TESTING... TESTING"
when i run the program, i get the output:

Code:

TESTING?

here's the whole thing:

Code:

#include <stdio.h>

int main() {
	char message[50];
	FILE *handle;
	handle = fopen("/Users/Jem/Desktop/test.txt","r");
	
	if (handle==NULL) {
		printf("Error opening file\n");
	}else {
		fscanf(handle,"%s",message);
		fclose(handle);
		printf("%s\n",message);
	}
	return 0;
}

1) %s will not read past a space. If you want to read a line which may include spaces, then fscanf is not for you. Look at fgets.

2) Did you type three actual periods, or do you have one of them fancy symbols in your file?

Originally Posted by tabstop

1) %s will not read past a space. If you want to read a line which may include spaces, then fscanf is not for you. Look at fgets.

2) Did you type three actual periods, or do you have one of them fancy symbols in your file?

Thanks. I typed three periods

I do not believe fopen will automatically expand the ~ variable into your home directory.

EDIT: Beaten!

handle is a FILE pointer, not a string you can print. Read the FAQ and the C File I/O tutorial.