strlen - calculate the length of a string
#include <string.h>
int strlen(string s);
#include <string.h>
size_t strlen(const char *s);
This function calculates the length of s.
The strlen() function calculates the length of the string pointed to by s, excluding the terminating null byte ('\0').
This function returns the number of characters in s, excluding the terminating NUL byte (i.e., '\0').
The strlen() function returns the number of characters in the string pointed to by s.
```c
#include
int main(void) { string s = get_string(“Input: “); printf(“Output: “); for (int i = 0, n = strlen(s); i < n; i++) { printf(“%c”, s[i]); } printf(“\n”); }
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
| strlen() | Thread safety | MT-Safe |
POSIX.1-2001, POSIX.1-2008, C89, C99, C11, SVr4, 4.3BSD.
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