ERROR: variable "string" is not initialized

Question

I wrote this code that reads from a .txt a string and settles it in a char *, but it gives me error that the variable "string" is not initialized, even if i initialized it inside the fscanf, can u tell me where i wrong? Thanks!

    char *string;
    FILE *fp = fopen("words.txt", "r");
    fscanf(fp, "%s", string);

well, if i dont know how is long the string in the txt file? How i allocate enough space for it? Thanks — wing
– wing, Commented Jun 10, 2015 at 12:54
string is a pointer to char. You've to make it point to a char array(char buffer[100]; string = buffer;) or dynamically allocate memory(string = malloc(100); and after use, free(string);) before you write to it from the fscanf. — Spikatrix
– Spikatrix, Commented Jun 10, 2015 at 12:54
If you don't know how long the text is then you have options. One is to figure out a maximum, 4096 is a common one used for a maximum line length. Second, don't use fscanf, use fread where you can specify the maximum number of bytes to read. That's a bit more work, but safer. — cdarke
– cdarke, Commented Jun 10, 2015 at 12:58
@wing , In that case, you can use getline if you can. It allocates the right amount of memory. — Spikatrix
– Spikatrix, Commented Jun 10, 2015 at 13:00

axellink · Accepted Answer · 2015-06-10 12:53:08Z

4

That's normal, you didn't allocate string. C needs you to allocate it in memory before you use it. Also you will have to know its size.

In your code, string points to nowhere into memory so it doesn't exist (to be exact it points to somewhere you have a lot of chance that you can't access it)

See how malloc works.

answered Jun 10, 2015 at 12:53

axellink

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Buddha · Accepted Answer · 2015-06-10 12:55:42Z

1

Allocate space for the string with malloc function.

string=malloc(100*sizeof(char));

edited Jun 10, 2015 at 12:55

answered Jun 10, 2015 at 12:52

Buddha

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3 Comments

skrtbhtngr Over a year ago

BTW, malloc is a function. "malloc statement" is a wrong statement.

cdarke Over a year ago

Perhaps you could explain where the 100 comes from?

Buddha Over a year ago

I just used 100 as an example.We can allocate as much memory as we feel safe to work with.

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