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

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

#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);

illumos DDI specific (illumos DDI).

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()all alter their first argument. Additionally, the strcpy() function does not check for overflow of the array.

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.

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;

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.

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.

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;

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).

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

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.

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.

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.

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.

See attributes(7) for descriptions of the following attributes:

ATTRIBUTE TYPE ATTRIBUTE VALUE
Interface Stability Committed

string(3C), attributes(7), bcopy(9F), ddi_copyin(9F), kmem_alloc(9F)

Writing Device Drivers

If copying takes place between objects that overlap, the behavior of strlcat(), strncat(), strcpy(), strlcpy(), and strncpy() is undefined.
May 20, 2022 OmniOS