Adding spaces to existing file

This is a discussion on Adding spaces to existing file within the C Programming forums, part of the General Programming Boards category; I'm with CommonTater, two files should be used. here is some code that will read, find and replace, then remove ...

  1. #16
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    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;
    }

  2. #17
    843
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    Quote Originally Posted by nonoob View Post
    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.

  3. #18
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    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*.

  4. #19
    843
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    My eyes must be deceiving me. Which part changed?

  5. #20
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    Code:
    $ cat file2.txt
    this is a test file
    ust for testing only
    bye bye...
    
    $ cc rw.c
    $ ./a.out
    File processing complete.
    $ cat file2.txt
    this is a test file
    
    st for testing only
    
    ye bye...
    rw.c source code is exactly your code. copy and pasted.
    It's time to post your program output...
    Last edited by Bayint Naung; 11-27-2010 at 01:07 AM.

  6. #21
    843
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    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.

  7. #22
    843
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    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.

  8. #23
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    Quote Originally Posted by nonoob View Post
    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.

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