For example, in python, you can index strings like this
some_string = "hello"
substring = some_string[0:3]
and substring will be "hel"
however, in C, if I have
char some_string[] = {'h', 'e', 'l', 'l', 'o'};
Is there a way to get just
{'h', 'e', 'l'}
There is probably a very simple solution that I am overlooking, but I find it hard to think in two languages sometimes.
Not very simple, primarily because of memory management. You either need substring to be an array of sufficiently many characters, or need to allocate the memory dynamically. for example:
char *some_string = "hello";
char substring[4];
strncpy(substring,some_string,3);
substring[3]='\0';
or:
char *substring(char *s, int start, int len)
{
char *s2= malloc(len+1);
strncpy(s2, s+start, len);
s2[len]='\0';
return s2;
}
start <= strlen(s)), too. (plus: strncpy() makes no sense here. (it seldom does))
strncpy?strcpy() won't do because not till end-of-string may need to be copied. memcpy() could do. What is wrong with strncpy()?For starters this declaration of a character array
char some_string[] = {'h', 'e', 'l', 'l', 'o'};
does not contain a string.
You should write either
char some_string[] = {'h', 'e', 'l', 'l', 'o', '\0'};
or
char some_string[] = {"hello"};
or
char some_string[] = "hello";
The only way to get a substring is to copy the sub-range of characters in another character array.
for example
#include <string.h>
// ...
char substring[4];
strncpy( substring, some_string, 3 );
substring[3] = '\0';
memcpy rather than strncpy here.
some_stringis not a C string. It lacks the null-terminator.