Thread: Adding spaces to existing file

I'm with CommonTater, two files should be used. here is some code that will read, find and replace, then remove the input file and rename the output file to the input.
Disclaimer: i haven't tested this yet. Correct me if i'm wrong

Code:

#include <stdio.h>

int main(int argc, char** argv) /* you don't need these args, but i like putting them in regardless */
{
	char line[255]; /* or however long you want */
	FILE* in = fopen("file2.txt", "r");
	FILE* out = fopen("_file2_.txt", "w");
	if (in == NULL) 
	{ 
		printf("File access error.\n");
		return 0;
	}
	while(fgets(line, sizeof line, INSTREAM) != NULL) /* if you only have 1 line, you can comment this out, but if the file contains multiple lines, leave this in */
	{
		for(i = 0; line[i] != NULL; i++)
		{
			if (line[i] == "#") /* finds "#" */
			{
				fprintf(out, "%c", "*";	/* writes "*" */
			}
			else
			{
				fprintf(out, "%c", line[i]); /* writes the letter that isn't "#" */
			}
		}
	}
	fclose(in); fclose(out);
	remove("file2.txt"); /* deletes the input file */
	rename("_file2_.txt", "file2.txt"); /* names the output file, what the input file was */
	return 0;
}

Originally Posted by nonoob

Oh wow, man. Reading a char, then immediately writing it... I have no idea if the system keeps separate file positions for read vs. write. I doubt it. So you may be duplicating a character into the NEXT position. Then you're backing up one, writing it again (why?), then writing a subsequent one. I think you need to relax and figure out what you're trying to accomplish.

Reading and writing uses the same position? That still doesn't explain why the file doesn't change. I mean, it still should have changed (new lines, spaces, deletions, etc.) but it doesn't.

Reading and writing uses the same position? That still doesn't explain why the file doesn't change. I mean, it still should have changed (new lines, spaces, deletions, etc.) but it doesn't.

The file is not changed at all?
I don't believe that. I compiled and run your code(post #1 code). The file is *changed*.

My eyes must be deceiving me. Which part changed?

Are you on Linux? Perhaps it's a compiler problem.

Code:

#include <stdio.h>

int main ()
{
	FILE *f1;
	int ch;

	f1 = fopen("file2.txt", "r+");

	if (f1 == NULL)
	{
		printf("File access error.\n");
		return;
	}

    while((ch = fgetc(f1)) != EOF)
	{
        printf("%c", ch);
	}

	rewind(f1);

	while((ch = fgetc(f1)) != EOF)
	{
		if (ch == '\n')
		fputc('\n', f1);
	}

	printf("\n\nFile processing complete.\n\n");

	rewind(f1);

	while((ch = fgetc(f1)) != EOF)
	{
        printf("%c", ch);
	}

    if (fclose(f1) != 0)
    printf("File close error.\n");

	return 0;
}

The output:

Code:

aaaaa
aaaaa
aaaaa

File processing complete.

aaaaa
aaaaa
aaaaa
Process returned 0 (0x0)   execution time : 0.011 s
Press any key to continue.

When I switch to the two-file system, the algorithm works correctly, so I suppose I'll do just that, now that I know how to remove and rename files. Thanks, guys.

Originally Posted by nonoob

Oh wow, man. Reading a char, then immediately writing it... I have no idea if the system keeps separate file positions for read vs. write. I doubt it.

It doesn't.