how repeat a string in language C - c

Question

how I do to repeat a string?
something like "hello world" * 3
the output "hello world hello world hello world"

Answer 1

In your source code, without much processing, probably the easiest way is with:
#define HI "hello world"
char str[] = HI " " HI " " HI;
This will declare a string of the requested value:
"hello world hello world hello world"
If you want code that will do it, you can use something like:
char *repeatStr (char *str, size_t count) {
if (count == 0) return NULL;
char *ret = malloc (strlen (str) * count + count);
if (ret == NULL) return NULL;
strcpy (ret, str);
while (--count > 0) {
strcat (ret, " ");
strcat (ret, str);
}
return ret;
}
Now keep in mind this can be made more efficient - multiple strcat operations are ripe for optimisation to avoid processing the data over and over (a). But this should be a good enough start.
You're also responsible for freeing the memory returned by this function.
(a) Such as with:
// Like strcat but returns location of the null terminator
// so that the next myStrCat is more efficient.
char *myStrCat (char *s, char *a) {
while (*s != '\0') s++;
while (*a != '\0') *s++ = *a++;
*s = '\0';
return s;
}
char *repeatStr (char *str, size_t count) {
if (count == 0) return NULL;
char *ret = malloc (strlen (str) * count + count);
if (ret == NULL) return NULL;
*ret = '\0';
char *tmp = myStrCat (ret, str);
while (--count > 0) {
tmp = myStrCat (tmp, " ");
tmp = myStrCat (tmp, str);
}
return ret;
}

Answer 2

You could use sprintf.
char s[20] = "Hello";
char s2[20];
sprintf(s2,"%s%s%s",s,s,s);

Answer 3

I've made this function based on earlier answers in this post.
I share it here because some of previous examples has been thrown me segfaults
const char* str_repeat(char* str, size_t times)
{
if (times < 1) return NULL;
char *ret = malloc(sizeof(str) * times + 1);
if (ret == NULL) return NULL;
strcpy(ret, &str);
while (--times > 0) {
strcat(ret, &str);
}
return ret;
}

Answer 4

http://ideone.com/5sNylW
#include <stdio.h>
#include <string.h>
int main(void) {
char k[100];
gets(k);
int lk=strlen(k);
int times;
scanf("%d",&times);
int tl= times*lk;
int i,x=0;
for(i=lk-1;i<tl;i++)
{
k[i+1]=k[x];
x++;
}
for(i=0;i<tl;i++)
{
printf("%c",k[i]);
}
return 0;
}

Answer 5

You may try write own function. It will be work with single-length string also (i. e. duplication a single char). It use the function "strcat()" from the "string.h", so do not forget include this header.
char *
str_repeat(char str[], unsigned int times)
{
if (times < 1)
return NULL;
char *result;
size_t str_len = strlen(str);
result = malloc(sizeof(char) * str_len + 1);
while (times--) {
strcat(result, str);
}
return result;
}
But, if you need only duplication of a string for print it, try macro
#define PRINT_STR_REPEAT(str, times) \
{ \
for (int i = 0; i < times; ++i) \
printf("%s", str); \
puts(""); \
}
Results
PRINT_STR_REPEAT("-", 10); // ----------
puts(str_repeat("-", 10)); // ----------
PRINT_STR_REPEAT("$", 2); // $$
puts(str_repeat("$", 2)); // $$
PRINT_STR_REPEAT("*\t*", 10); // * ** ** ** ** ** ** ** ** ** *
puts(str_repeat("*\t*", 10)); // * ** ** ** ** ** ** ** ** ** *
PRINT_STR_REPEAT("*_*", 10); // *_**_**_**_**_**_**_**_**_**_*
puts(str_repeat("*_*", 10)); // *_**_**_**_**_**_**_**_**_**_*

Answer 6

Here's a way to repeat a string in C, N times.
That is have a string "abc"
and I want a string of length 7 that is comprised of this string repeated.
N = 7;
result: "abcabca"
while(Index != N){
repeatedString[Index] = oldString[Index%strlen(oldString)];
Index++;
}
Where repeated String would be "abcabca" at the end, and oldString is "abc".