use of scanf()

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Re: use of scanf()

 
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  #21
Sep 25th, 2006
also the program is showing no compilation error, onlyruntime segmentation error is there...
i am working in linux
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Re: use of scanf()

 
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  #22
Sep 25th, 2006
> scanf("%s", &retry);
First buffer overflow - retry is a single char, you can't put a string into a single char.
Second problem, calling a function recursively just to implement a while loop is poor form.
Third, you're mixing scanf() with fgets(), which will surely lead to trouble at some point.

Separate the function into two steps
- readInput
- TokeniseInput.

Both will be a lot simpler than what you have at the moment.
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Re: use of scanf()

 
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  #23
Sep 26th, 2006
So i will have to declare my variables global..
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Re: use of scanf()

 
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  #24
Sep 26th, 2006
it didn't work . i think the segmentation error is because of some logical error not because of scanf(), gets() problem
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Re: use of scanf()

 
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  #25
Sep 26th, 2006
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Originally Posted by rati View Post
it didn't work . i think the segmentation error is because of some logical error not because of scanf(), gets() problem
Thats why we insist to post the code or if you cant, then U need to reconstruct the problem in smaler code. The post I posted don't give seg error, if U don't belive me compile and run the code which I posted.
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Re: use of scanf()

 
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  #26
Sep 27th, 2006
C Syntax (Toggle Plain Text) 
  1. //# include<stdio.h>
  2. void function();
  3. main()
  4. {
  5. function();
  6. }
  7. void function()
  8. {
  9.    int i,index,k,m;
  10.    char str1[100],retry,str[100],*ptr,*ctr;
  11.    int j=0;
  12.    printf("enter the string");
  13.    fgets(str, sizeof(str), stdin);
  14.    if((ptr = strchr(str, '\n')) != NULL)
  15.       *ptr = '\0';
  16.    printf("enter the string to be compared");
  17.    fgets(str1, sizeof(str1) , stdin);
  18.    if((ctr = strchr(str1, '\n')) != NULL)
  19.       *ctr = '\0';
  20.    /* printf("enter index"); */
  21.    /* canf("%d",& index); */
  22.    char *ch,*pch;
  23.    ch=strtok(str,":");
  24.    printf(" ratg");
  25.    if (ch==NULL)
  26.    {
  27.       printf("entered string is incorrect,reenter? y/n");
  28.       scanf("%s",&retry);
  29.       if(retry=='y')
  30.          function();
  31.       else return;
  32.    }
  33.    else
  34.       printf("\nch is NULL\n");
  35.    while(ch!=NULL)
  36.    {
  37.    pch=strstr(ch,";");
  38.    i=pch-ch;
  39. /*   strncpy(tr[j].member1,ch,i); */
  40. /*   strcpy(tr[j].member2,pch+1); */
  41.    j++;
  42.    ch=strtok(NULL,":");
  43.    }


i tried your code . yes it is not giving any segmentation error but it is not performing desired operation
first of all it is giving a warning:
assignment makes pointer from integer without a cast
for statements 23 and 42
then it is not going inside the loop for asking the user if he wants to enter again the string

i am working on linux , i hope this is not creating any problems

i will be posting a reconstructed program of mine for your convinience
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Re: use of scanf()

 
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  #27
Sep 27th, 2006
C Syntax (Toggle Plain Text) 
  1. // # include<stdio.h>
  2. void function();
  3. main()
  4. {
  5. function();
  6. }
  7. void function()
  8. {
  9.    int i,index,k,m;
  10.    char str1[100],retry,str[100],*ptr,*ctr;
  11.    int j=0;
  12.    printf("enter the string");
  13.    fgets(str, sizeof(str), stdin);
  14.    if((ptr = strchr(str, '\n')) != NULL)
  15.       *ptr = '\0';
  16.    printf("enter the string to be compared");
  17.    fgets(str1, sizeof(str1) , stdin);
  18.    if((ctr = strchr(str1, '\n')) != NULL)
  19.       *ctr = '\0';
  20.    /* printf("enter index"); */
  21.    /* canf("%d",& index); */
  22.    char *ch,*pch;
  23.    ch=strtok(str,":");
  24.    printf(" ratg");
  25.    if (ch==NULL)
  26.    {
  27.       printf("entered string is incorrect,reenter? y/n");
  28.       scanf("%s",&retry);
  29.       if(retry=='y')
  30.          function();
  31.       else return;
  32.    }
  33.    else
  34.       printf("\nch is NULL\n");
  35.    while(ch!=NULL)
  36.    {
  37.    pch=strstr(ch,";");
  38.    i=pch-ch;
  39. /*   strncpy(tr[j].member1,ch,i); */
  40. /*   strcpy(tr[j].member2,pch+1); */
  41.    j++;
  42.    ch=strtok(NULL,":");
  43.    }
  44.      }



i tried your code but it is not giving desired result, it is not asking the user if he wants to reenter
also there are warnings for statements 23 and 42
assignment makes pointer from integer without a cast

i am working on linux , i hope that is not causing any problem

i am working on reconstruction of the code for your convinience
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Re: use of scanf()

 
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  #28
Sep 27th, 2006
C Syntax (Toggle Plain Text) 
  1. //# include<stdio.h>
  2. # include <string.h>
  3. # include<stdlib.h>
  4. void function(char *);
  5. int j;
  6. struct test
  7. {
  8. char member1[20];
  9. char member2[20];
  10. };
  11. struct test *tr;
  12. int main()
  13. {
  14. char str[100];
  15. printf("enier the string");
  16. scanf("%s",&str);
  17. tr=(struct test *)malloc( sizeof (struct test)*100);
  18. function(str);
  19. free(tr);
  20. return 0;
  21. }
  22. void function(char * str)
  23. {
  24. long int i,index,k;
  25. char str1[100],*ch,*pch;
  26. j=0;
  27. ch=strtok(str,":");
  28. if (ch==NULL)exit(0);
  29. while(ch!=NULL)
  30. {
  31. pch=strstr(ch,";");
  32. i=pch-ch;
  33. strncpy(tr[j].member1,ch,i);
  34. strcpy(tr[j].member2,pch+1);
  35. j++;
  36. ch=strtok(NULL,":");
  37. };
  38. for(k=0;k<j;k++)
  39. {
  40. printf("\n%s",tr[k].member1);
  41. printf("\n%s",tr[k].member2);}
  42. }
this is my code
it gives desired output when string entered is nghg;jhjkh:kjhkh;mhjkh
but gives segmentatiopn error for hjghjgjg
it should exit from the program for such a string
Last edited by rati; Sep 27th, 2006 at 3:36 am. Reason: code written in incorrect way
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Re: use of scanf()

 
1
  #29
Sep 27th, 2006
The seg fault is becouse if you dont have ';' then pch is NULL. So seg fault will happen only if you dont have ';' in the input string. You need to change the logic
C Syntax (Toggle Plain Text) 
  1. #include<stdio.h>
  2. #include <string.h>
  3. #include<stdlib.h>
  4. void function(char *);
  5. int j;
  6. struct test
  7. {
  8.    char member1[20];
  9.    char member2[20];
  10. };
  11. struct test *tr;
  12. int main()
  13. {
  14.    char str[100], *ptr;
  15.    printf("enter the string: ");
  16.    /* scanf("%s",&str); */
  17.    fgets(str, sizeof(str), stdin);
  18.    if((ptr = strchr(str, '\n')) != NULL)
  19.       *ptr = '\0';
  20.    tr=(struct test *)malloc( sizeof (struct test)*100);
  21.    function(str);
  22.    free(tr);
  23.    return 0;
  24. }
  25. void function(char * str)
  26. {
  27.    long int i,index,k;
  28.    char str1[100],*ch = NULL,*pch = NULL;
  29.    j=0;
  30.    tr->member1[0] = '\0';
  31.    tr->member2[0] = '\0';
  32.  
  33.    ch=strtok(str, ":");
  34.    printf("*ch = %c\n", *ch); /* debug print */
  35.    if (ch==NULL)
  36.       exit(0);
  37.    while(ch!=NULL)
  38.    {
  39.       pch=strstr(ch,";");
  40.       if (pch == NULL)
  41.       {
  42.          ch=strtok(NULL,":");
  43.          continue;
  44.       }
  45.       printf("*pch = %c\n", *pch); /* debug print */
  46.       i=pch-ch;
  47.       printf("i = %ld\n", i);
  48.       strncpy(tr[j].member1,ch,i);
  49.       strcpy(tr[j].member2,pch+1);
  50.       j++;
  51.       ch=strtok(NULL,":");
  52.    }
  53.    for(k=0;k<j;k++)
  54.    {
  55.       printf("\n%s",tr[k].member1);
  56.       printf("\n%s",tr[k].member2);
  57.    }
  58. }
Run this
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Re: use of scanf()

 
1
  #30
Sep 27th, 2006
Right now i am testing for ch, and before pch tests for ; ch is null
so the program should end there itself when ch is null, why would it continue till pch??
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