sprintf giving me issues

This is a discussion on sprintf giving me issues within the C Programming forums, part of the General Programming Boards category; You can use "%02d" format or don't use sprintf at all Code: #include <string.h> #include <stdio.h> int main(int argc, char* ...

  1. #16
    CSharpener vart's Avatar
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    You can use "%02d" format

    or don't use sprintf at all

    Code:
    #include <string.h>
    #include <stdio.h>
    
    int main(int argc, char* argv[])
    {
    	char modelName [] = "modelB.xx";
    	int len = strlen(modelName);
    	char a;
    	char b;
    
    	for(a='0';a<= '9'; a++)
    	{
    	   for(b='0';b<='9';b+=5)
    	   {
    		  modelName[len-2] = a;
    		  modelName[len-1] = b;
    		  printf("%s\n",modelName);
    	   }
    	}
    	return 0;
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  2. #17
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    I re-read you post and may not really understand what you want your output to look like.

    show an example

    like 5 should be?
    modelname.05

    modelname.500?

    modelname.0500?

  3. #18
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    Ah, works like a charm--thanks so much! Now, when I try to open the file, it doesn't quite work. I know I'm pointing to the right location because the file does open when, after all that code, I say modelfile=(string with the right file name), where that string is exactly the same as what I created (modelname.xx). Any idea what the problem is here? Code:
    Code:
    for (i = 0; i <= 90; i += 5) { //Loops through all inclinations.
             if (i < 10) {
                   sprintf(inc, "0%d", i);
             } else {
                    sprintf(inc, "%d", i);
             }
             modelfile = malloc(strlen(modelname) + strlen(inc) + strlen("Lightcurves\\") + 1);
             sprintf(modelfile, "%s%s%s%s", "Lightcurves\\", modelname, inc, ".mag");
             printf("%s\n", modelfile); //String 1
             modelfile="Lightcurves\\modelB.00.mag";
             printf("%s\n", modelfile); //String 2, appears exact same as String 1
             model = fopen(modelfile, mode); //This opens the file properly with String 2 but NOT when I use string 1.
    if (model == NULL) { //Error handling.
    fprintf(stderr, "Can't open input file!\n");
    system("pause");
    exit(1);
    } else {
    printf("File opened successfully.\n");
    }
    system("pause");
             free(modelfile);
         } //Ends loop.

  4. #19
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    Erm, if I'm not being totally clear here, basically the issue is that when I create the string by adding together different bits, it doesn't find the file, but when I create the same string by typing it in manually, it does find the file. I would type them all in manually but that would be kind of unwieldy since I'd need to create an array of 19 similar strings ("Lightcurves\\modelB.00.mag", etc.).

  5. #20
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    int main (void) {
            int i;
            char *modelfile;
            char modelname[] = "modelname.";
            char inc[3];
            FILE *fp;
    
            modelfile = malloc(strlen(modelname) + 4);
    
            for (i = 0; i < 99; i += 5)
            {
                    if (i < 10)
                            sprintf(inc, "0%d", i);
                    else
                            sprintf(inc, "%d", i);
    
            sprintf(modelfile, "%s%s", modelname, inc);
            printf("%s\n", modelfile);
    
            if ((fp = fopen(modelfile, "w")) == NULL)
            {
                    perror("Crap");
                    exit(1);
            }
    
            fprintf(fp, "wrote to file");
    
            }
    
            fclose(fp);
            free(modelfile);
            return 0;
    }
    this wrote to the files fine for me
    each one had the "wrote to file message"

  6. #21
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    Yes, but I'm trying to read files that already exist, not write to new ones. It's not finding the files when I build the string, but it is finding them when I type in the same string manually.

  7. #22
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    should work, I just changed my fopen to open the files for reading....then used fgets, to read a line
    and it read each file fine.

    Code:
            if ((fp = fopen(modelfile, "r")) == NULL)
            {
                    perror("Crap");
                    exit(1);
            }
    
            fgets(data, 14, fp);
            printf("%s\n", data);
    should tidy up your code a bit so its easier to read...add some whitespace etc.

  8. #23
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    OK, new development, so this always fails the first time through, but then on subsequent loops, it opens up the file just fine....

  9. #24
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    OK! I've slightly (haha, slightly...) modifed my code. The good news is, it compiles and then opens up all the files! The bad news is, even though it compiles and runs, I get warnings when I compile. Here's the new code:

    Code:
    void fitCurves()
    {
         int i;
         char inc[3];
         char *modelfile[19][20];
         char *temp;
         out = fopen("bestinc.txt", "a+"); //Opens file to write results to.
         fprintf(out, "i\tX^2\n"); //Prints header in periods.txt.
         for (i = 0; i <= 90; i += 5) {
             sprintf(inc, "%02d", i);
             temp = malloc(strlen(modelname) + strlen(inc) + strlen("Lightcurves\\") + 1);
             sprintf(temp, "%s%s%s%s", "Lightcurves\\", modelname, inc, ".mag");
             strcpy(modelfile[i/5], temp);
             free(temp);
         }
         for (i = 0; i <= 90; i += 5) { //Loops through all inclinations.
             printf("%s\n", modelfile[i/5]);
             model = openFile(modelfile[i/5]);
             fclose(model);
         } //Ends loop.
    }
    Where openFile is a function I defined elsewhere to open the file and let me know if it was successful or not. So I changed my approach from doing everything at once to creating an array of strings, each with a different file name, so that in my second loop, I just open the appropriate file. The warnings I get are:

    70 C:\(personal)\EX5.c [Warning] passing arg 1 of `strcpy' from incompatible pointer type (for the strcopy)
    75 C:\(personal)\EX5.c [Warning] passing arg 1 of `openFile' from incompatible pointer type (for the model=openFile line)

    Any ideas why I'm getting these even though it compiles, and how to fix them without changing the functionality? Thanks!

  10. #25
    CSharpener vart's Avatar
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    Code:
         char *modelfile[19][20];
    remove *

    Code:
             temp = malloc(strlen(modelname) + strlen(inc) + strlen("Lightcurves\\") + 1);
             sprintf(temp, "%s%s%s%s", "Lightcurves\\", modelname, inc, ".mag");
    no place for ".mag" - memory overrun

    No checks for null pointers - you should check the values returned by the functions you call. They not always work as supposed, sometimes - errors occur
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  11. #26
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    But I need the * so I can pass it to fopen()...when I remove the * from *modelfile I get a few problems, most importantly that it no longer opens the files. Also...which functions should I be checking null pointers for? Would that get rid of my warnings?

  12. #27
    CSharpener vart's Avatar
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    fopen awaits const char*
    in your case modelfile[i/5] has a type of char*[] == pointer to array of chars not a pointer to char.

    So no - you don't need a * to pass the modelfile[i/5] to the fopen function.

    which functions should I be checking null pointers for
    You are using not so many functions in your code, just read the manual about each one - the return value and possible errors part.
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  13. #28
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    Thanks so much! Sorry to keep asking questions but I'm not 100% sure how to fix this here...it crashes (at some point in the program) when I try declaring modelfile as either:

    char *modelfile[19];

    or

    char modelfile[19][20];

    So I really think my declaration is right. Is there a way to, just for the purposes of fopen, convert the char*[] to a char*? My main language is Java so this new way of handling strings (through chars) is still pretty strange to me...

  14. #29
    CSharpener vart's Avatar
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    So I really think my declaration is right.
    You wrong. The crash has other source - you do not use the memory in the right way. When you copy string - you do not check that there is enough memory for it.
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  15. #30
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    OK...so how do I go about fixing this? Like I said, I'm fairly new to C, I'm not sure how it all works yet...

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