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Managing strings, renaming problems

This is a discussion on Managing strings, renaming problems within the C Programming forums, part of the General Programming Boards category; Hi, I'd like to make a program which does this renaming work: example.txt -> example(copy).txt Also, I'd like it to ...

  1. #1
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    Managing strings, renaming problems

    Hi, I'd like to make a program which does this renaming work:

    example.txt -> example(copy).txt

    Also, I'd like it to support any number of '.' into the file name, like:

    example.2011.txt -> example.2011(copy).txt

    I've tried using string.h functions... and I didn't think it could be that hard.

    I don't need help about the file managing (fopen, rename, etc). I just need help finding the correct position where to add the "(copy)".

    I've been working on it for some hours... then I decided to ask here because probably the code became too complex for the simple work.

    Here it is:
    Code:
    #include <stdio.h>
    #include <string.h>
    
    int main(int argc, char *argv[])
    {
    	char **ppc; // to visit **argv
    	char *est; // where to attach strings' extension
    	char *result; // resultant filename
    	int dim; // string length
    	int dim2; // 2nd string length
    	int i; // this serves like an index
    	int i2; // used to find filename's first part, then to copy the extension part
    	int i3;
    
        if(argc > 1)
        {
        	ppc = argv + 1;
        	for(i = 1; i < argc; ++i)
        	{
        		printf("%s renamed to ", *ppc);
    			dim = strlen(*ppc);
    			est = strrchr(*ppc, '.');
    			i2 = est - *ppc;
    			printf("\ni2 = %d (number of letters before the last '.')\n", i2);
    			result = strncpy(result, *ppc, i2);
    			printf("\nresult: %s\n", result);
    			i3 = i2 = dim - i2;
    			printf("\ni2: %d\n", i2);
    			while(i2-- > 0)
    			{
    				printf("%c", *est++);
    				//est++;
    				//*est = *est;
    				//*(++est) = *(est+1);
    			}
    			//est = est - i2
    			*(est) = '\0';
    			est = est - i3;
    			printf("\nextension: %s\n", est);
    			dim2 = strlen(est);
    			//result = strncpy(result, *ppc, dim - dim2);
    			result = strcat(result, "(copy)");
    			result = strcat(result, est);
    			printf("%s\n", result);
        	}
    	}
    
        return 0;
    }
    If you are on *nix, you can use the terminal and try "./binaryname example.txt" and it will work. But when I tried "./binaryname example.2011.txt" it printed some weird characterhs through the name.

    Where do I make errors?
    Thank you

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    Code:
    	char *result; // resultant filename
    If you are going to use result as though it pointed somewhere useful (such as, say, "result = strncpy(result, *ppc, i2);"), then you should make sure that it does, in fact, point somewhere useful.

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    Quote Originally Posted by tabstop View Post
    Code:
    	char *result; // resultant filename
    If you are going to use result as though it pointed somewhere useful (such as, say, "result = strncpy(result, *ppc, i2);"), then you should make sure that it does, in fact, point somewhere useful.
    Ehm... what's wrong with that "result = strncpy(result, *ppc, i2);" ? In that part i want it to point to the "first part" of the filename, the part which is before the (copy) string (which I add it on the last part).
    If you wanted to tell me something else, please write it again in another form maybe I don't get it due to english problems.

    Thanks!

    edit: maybe I got it. When I use strncpy, does it allocate the space and assign it to result... or not?? Is this the problem?
    Last edited by kr0n1x; 09-02-2011 at 10:50 PM.

  4. #4
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by kr0n1x View Post
    edit: maybe I got it. When I use strncpy, does it allocate the space and assign it to result... or not?? Is this the problem?
    strncpy does no space allocating at all.

  5. #5
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    Quote Originally Posted by tabstop View Post
    strncpy does no space allocating at all.
    Yay I got it

    #include malloc.h

    then, right before the strncpy instruction, I put:
    result = malloc(i2);

    Now it seems to work thanks! I will complete it for multiple files.

    Rhetorical question: Is there a better way to do this job? How?

    I'm curious to see how simple this could be... and learn more

  6. #6
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by kr0n1x
    #include malloc.h
    No, that should be #include <stdlib.h>
    CommonTater likes this.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  7. #7
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    Quote Originally Posted by laserlight View Post
    No, that should be #include <stdlib.h>
    Oh... at the university my professors taught me wrong.
    I didn't know that it contained malloc too... I'm reading on wikipedia right now.

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