I have a chunk of memory I'm declaring on the heap.
char *str;
str = (char *)malloc(sizeof(char) * 10);
I have a const string.
const char *name = "chase";
Because *name
is shorter than 10
I need to fill str
with chase
plus 5 spaces.
I've tried to loop and set str[i] = name[i]
but there's something I'm not matching up because I cannot assign spaces to the additional chars. This was where I was going, just trying to fill str
with all spaces to get started
int i;
for (i = 0; i < 10; i++)
{
strcpy(str[i], ' ');
printf("char: %c\n", str[i]);
}
As the others pointed out, you need
//malloc casting is (arguably) bad
str = malloc(sizeof(char) * 11);
and then, just do
snprintf(str, 11, "%10s", name);
Using snprintf()
instead of sprintf()
will prevent overflow, and %10s
will pad your resulting string as you want.
If you want str
to have 10 characters and still be a C-string, you need to '\\0'
terminate it. You can do this by malloc
ing str
to a length of 11:
str = malloc(11);
Note there's no need to cast the return pointer of malloc
. Also, sizeof(char)
is always 1 so there's no need to multiply that by the number of char
s that you want.
After you've malloc
as much memory as you need you can use memset
to set all the char
s to ' '
(the space character) except the last element. The last element needs to be '\\0'
:
memset(str, ' ', 10);
str[10] = '\0';
Now, use memcpy
to copy your const
C-string to str
:
memcpy(str, name, strlen(name));
easy to use snprintf like this
#include <stdio.h>
#include <stdlib.h>
int main(){
char *str;
str = (char *)malloc(sizeof(char)*10+1);//+1 for '\0'
const char *name = "chase";
snprintf(str, 11, "%-*s", 10, name);//11 is out buffer size
printf(" 1234567890\n");
printf("<%s>\n", str);
return 0;
}
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