convert element of char* to a character

This is a discussion on convert element of char* to a character within the C Programming forums, part of the General Programming Boards category; I've got a variable file of type char* , and am trying to iterate through a for loop by doing ...

  1. #1
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    Feb 2010
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    convert element of char* to a character

    I've got a variable file of type char*, and am trying to iterate through a for loop by doing the following:

    Code:
    int idx;
    for (idx=0; file[idx] != '\0'; idx++) {
      //do some stuff
    }

    The file[idx] part of the stop condition results in the error Segmentation fault (core dumped). I believe that I am not quite understanding something related to indexing and character pointers. Could someone shed some light on this for me? Thanks!

    I notice that couple of test lines preceeding this code:
    Code:
    printf("%c\n", file[0]);
    printf("%c\n", file[0]);
    do seem to be giving expected results. How can i translate file[idx] into a character that i can use in my stop condition?

  2. #2
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    Thumbs up

    I think you have not allocaetd the memory for the character pointer variable file.If you allocated memory for that variable you will not get segmentation fault.

    Use this,

    Code:
    #include<stdio.h>
    #include<malloc.h>
    #include<string.h>
    main()
    {
     char *file;
     file=malloc(100);
     strcpy(file,"Hello");
    int idx=0;
    for (idx=0; file[idx] != '\0'; idx++) {
            printf("%c",file[idx]);
    }
    }
    Thanks

  3. #3
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    All of this is going on within a function and unfortunately file is a variable for a function parameter. How could I resolve it in this case? Sorry, I probably should have mentioned that.

  4. #4
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    Post your entire code . It will helpful for others to understand the problem.

  5. #5
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    whoa! The problem was that my function char* parameter variable (which in this particular use case, takes a file passed by the user) was not null terminated. More surprising is that the string was followed by a bunch of private user and system environment info.

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