NAME
strlen strnlen
— get length of fixed size string
SYNOPSIS
#include
<string.h>
size_t strlen(const char *s); [CX] size_t strnlen(const char *s, size_t maxlen);
DESCRIPTION
For strlen (): [CX] The
functionality described on this reference page is aligned with the ISO C
standard. Any conflict between the requirements described here and the ISO C
standard is unintentional. This volume of POSIX.1-2017 defers to the ISO C
standard.
The strlen () function shall compute the
number of bytes in the string to which s points, not
including the terminating NUL character.
[CX] The strnlen () function shall compute the smaller of the number of bytes in the array to which s points, not including any terminating NUL character, or the value of the maxlen argument. The strnlen () function shall never examine more than maxlen bytes of the array pointed to by s.
RETURN VALUE
The strlen () function shall return the
length of s; no return value shall be reserved to indicate
an error.
[CX] The strnlen () function shall return the number of bytes preceding the first null byte in the array to which s points, if s contains a null byte within the first maxlen bytes; otherwise, it shall return maxlen.
ERRORS
No errors are defined.
EXAMPLES
Getting String Lengths
The following example sets the maximum length of
key and
data by
using strlen () to get the lengths of those
strings.
#include <string.h>
...
struct element {
char *key;
char *data;
};
...
char *key, *data;
int len;
*keylength = *datalength = 0;
...
if ((len = strlen(key)) > *keylength)
*keylength = len;
if ((len = strlen(data)) > *datalength)
*datalength = len;
...
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
XBD <string.h>
CHANGE HISTORY
First released in Issue 1. Derived from Issue 1 of the SVID.
Issue 5
The RETURN VALUE section is updated to indicate that
strlen () returns the length of s,
and not s itself as was previously stated.
Issue 7
The strnlen () function is added from The Open Group Technical Standard, 2006, Extended API Set Part 1.
POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0344 [560] is applied.