Assigning a char pointer to char array in C

Question

I am starting to studying C and I already run into few problems. I want to parse a file and store the results of each line in a structure. My structure looks like:

struct record {
    char x[100];
}

Then, whenever I use strtok to parse a line in some file.txt,

struct record R;
...
char *token;
token = strtok(line, "\t");

token returns a pointer to the string and whenever I print it, it is correct string. I want to assign token to x, such as R.x = token, but I get an error, "char x[100] is not assignable". Is it possible to convert this pointer token to actual char array or what would be the best way to store the results into the structure?

You cannot assign arrays like that. Use memcpy() to fill it with the data you want it to contain. — Bregalad
– Bregalad, Commented Apr 11, 2015 at 7:07

Spikatrix · Accepted Answer · 2015-04-11 07:07:28Z

5

The error says it all. Arrays are not assignable. You need to copy each character one by one and then append a NUL-terminator at the end.

Fortunately there is a function that does this for you. The name of the function is strcpy and it is found in the string.h header.

To fix your issue, use

strcpy(R.x,token);

instead of

R.x = token;

answered Apr 11, 2015 at 7:07

Spikatrix

20.3k7 gold badges44 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

August Karlstrom · Accepted Answer · 2015-04-11 12:25:59Z

1

Use strcpy after making sure that the string fits in the array:

#define LEN(array) (sizeof (array) / sizeof (array)[0])

if (strlen(token) < LEN(R.x)) {
   strcpy(R.x, token);
} else {
   fprintf(stderr, "error: input string \"%s\" is longer than maximum %d\n", token, LEN(R.x) - 1);
}

answered Apr 11, 2015 at 12:25

August Karlstrom

11.4k8 gold badges45 silver badges70 bronze badges

Comments

Shihe Zhang · Accepted Answer · 2017-05-03 06:38:15Z

1

strcpy stops when it encounters a NULL, memcpy does not. So if you array have 0x00 eg. \0 in middle,you should use memcpy rather than strcpy.

answered May 3, 2017 at 6:38

Shihe Zhang

2,7815 gold badges40 silver badges58 bronze badges

Collectives™ on Stack Overflow

Assigning a char pointer to char array in C

3 Answers 3

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related