illumos: manual page: strlen.9f

STRING(9F) Kernel Functions for Drivers STRING(9F)

NAME

string, strcasecmp, strncasecmp, strcat, strncat, strlcat, strchr,
strrchr, strcmp, strncmp, strcpy, strncpy, strlcpy, strfree, strspn,
strdup, ddi_strdup, strlen, strnlen, strtok_r - string operations

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

int strcasecmp(const char *s1, const char *s2);

int strncasecmp(const char *s1, const char *s2, size_t n);

char *strcat(char * s1, const char * s2);

char *strncat(char * s1, const char * s2, size_t n);

size_t strlcat(char *dst, const char *src, size_t dstsize);

char *strchr(const char *str, int chr);

char *strrchr(const char *str, int chr);

int strcmp(const char *s1, const char *s2);

int strncmp(const char *s1, const char *s2, size_t n);

char *strcpy(char * dst, const char * src);

char *strncpy(char * dst, const char * src, size_t n);

size_t strlcpy(char *dst, const char *src, size_t dstsize);

void strfree(char *s);

size_t strspn(const char *s1, const char *s2);

char *strdup(const char *s1);

char *ddi_strdup(const char *s1, int flag);

size_t strlen(const char *s);

size_t strnlen(const char *s, size_t n);

char *strtok_r(char *s1, const char *s2, char **lasts);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

DESCRIPTION

The arguments s, s1, and s2 point to strings (arrays of characters
terminated by a null character). The strcat(), strncat(), strlcat(),
strcpy(), strncpy(), strlcpy(), strfree(), and strtok_r() functions all
alter their first argument. Additionally, the strcpy() function does not
check for overflow of the array.

strcasecmp(), strncasecmp()
The strcasecmp() and strncasecmp() functions are case-insensitive
versions of strcmp() and strncmp() respectively, described below. They
assume the ASCII character set and ignore differences in case when
comparing lower and upper case characters.

strcat(), strncat(), and strlcat()
The strcat() function appends a copy of string s2, including the
terminating null character, to the end of string s1. The strncat()
function appends at most n characters of s2 to s1, not including any
terminating null character, and then appends a null character. Each
returns a pointer to the null-terminated result. The initial character of
s2 overrides the null character at the end of s1. If copying takes place
between objects that overlap, the behavior of strcat(), strncat(), and
strlcat() is undefined.

The strlcat() function appends at most (dstsize-strlen(dst)-1)
characters of src to dst (dstsize being the size of the string buffer
dst). If the string pointed to by dst contains a null-terminated string
that fits into dstsize bytes when strlcat() is called, the string pointed
to by dst will be a null-terminated string that fits in dstsize bytes
(including the terminating null character) when it completes, and the
initial character of src will override the null character at the end of
dst. If the string pointed to by dst is longer than dstsize bytes when
strlcat() is called, the string pointed to by dst will not be changed.
The function returns min{dstsize,strlen(dst)}+strlen(src). Buffer
overflow can be checked as follows:

if (strlcat(dst, src, dstsize) >= dstsize)
return -1;

strchr(), strrchr()
The strchr() function returns a pointer to the first occurrence of c
(converted to a char) in string s, or a null pointer if c does not occur
in the string. The strrchr() function returns a pointer to the last
occurrence of c. The null character terminating a string is considered to
be part of the string.

strcmp(), strncmp()
The strcmp() function compares two strings byte-by-byte, according to the
ordering of your machine's character set. The function returns an
integer greater than, equal to, or less than 0, if the string pointed to
by s1 is greater than, equal to, or less than the string pointed to by s2
respectively. The sign of a non-zero return value is determined by the
sign of the difference between the values of the first pair of bytes that
differ in the strings being compared. The strncmp() function makes the
same comparison but looks at a maximum of n bytes. Bytes following a null
byte are not compared.

strcpy(), strncpy(), strlcpy()
The strcpy() function copies string s2 to s1, including the terminating
null character, stopping after the null character has been copied. The
strncpy() function copies exactly n bytes, truncating s2 or adding null
characters to s1 if necessary. The result will not be null-terminated if
the length of s2 is n or more. Both the strcpy() and strncpy() functions
return s1. If copying takes place between objects that overlap, the
behavior of strcpy(), strncpy(), and strlcpy() is undefined.

The strlcpy() function copies at most dstsize-1 characters (dstsize
being the size of the string buffer dst) from src to dst, truncating
src if necessary. The result is always null-terminated. The function
returns strlen(src). Buffer overflow can be checked as follows:

if (strlcpy(dst, src, dstsize) >= dstsize)
return -1;

strfree()
The strfree() function frees the memory associated with the string
pointed to by s. This memory pointed to by s must be of size
strlen(s)+1, and must have been allocated (either directly or indirectly)
by kmem_alloc(9F) or kmem_zalloc(9F).

strspn()
The strspn() function returns the length of the initial segment of string
s1 that consists entirely of characters from string s2.

strdup(), ddi_strdup()
The ddi_strdup() function returns a pointer to a new string that is a
duplicate of the string pointed to by s1. The returned pointer can be
passed to strfree() or kmem_free(9F). The space for the new string is
obtained using kmem_alloc(). flag can be either KM_SLEEP or KM_NOSLEEP,
and determines whether the caller can sleep for memory. KM_SLEEP
allocations may sleep but are guaranteed to succeed. KM_NOSLEEP
allocations are guaranteed not to sleep but may fail (return NULL) if no
memory is currently available.

The strdup() function behaves the same as the ddi_strdup() when called
with the KM_SLEEP flag. This means that strdup() can sleep until memory
is available and will always succeed.

strlen(), strnlen()
The strlen() function returns the number of bytes in s, not including the
terminating null character.

The strnlen() function returns the smaller of n or the number of bytes in
s, not including the terminating null character. The strnlen() function
never examines more than n bytes of the string pointed to by s.

strtok_r()
The strtok_r() function considers the null-terminated string s1 as a
sequence of zero or more text tokens separated by spans of one or more
characters from the separator string s2. The argument lasts points to a
user-provided pointer which points to stored information necessary for
strtok_r() to continue scanning the same string.

In the first call to strtok_r(), s1 points to a null-terminated string,
s2 to a null-terminated string of separator characters, and the value
pointed to by lasts is ignored. The strtok_r() function returns a pointer
to the first character of the first token, writes a null character into
s1 immediately following the returned token, and updates the pointer to
which lasts points.

In subsequent calls, s1 is a null pointer and lasts is unchanged from the
previous call so that subsequent calls move through the string s1,
returning successive tokens until no tokens remain. The separator string
s2 can be different from call to call. When no token remains in s1, a
null pointer is returned.

CONTEXT

The strdup() and ddi_strdup() functions can be called from user or kernel
context.

The ddi_strdup() function can be called from interrupt context only if
the KM_NOSLEEP flag is set.

All the other string manipulation functions can be called from user,
interrupt, or kernel context.

ATTRIBUTES

NOTES

If copying takes place between objects that overlap, the behavior of
strlcat(), strncat(), strcpy(), strlcpy(), and strncpy() is undefined.

March 19, 2025 STRING(9F)