string(3C)

Synopsis

   #include <string.h>
   

   char strcat(char s1, const char s2);
   

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

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

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

   char strcpy(char s1, const char s2);
   

   char strncpy(char s1, const char s2, size_t n);
   

   char strdup(const char s1);
   

   size_t strlen(const char s);
   

   char strchr(const char s, int c);
   

   char strrchr(const char s, int c);
   

   char strpbrk(const char s1, const char s2);
   

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

   size_t strcspn(const char s1, const char s2);
   

   char strtok(char s1, const char s2);
   

   char strtok_r(char s1, const char s2, char next);
   

   char strstr(const char s1, const char s2);

Description

strncat- append n characters of one string to another

strcmp- compare one string to another

strncmp- compare n characters of one string to another

strcpy- copy one string to another

strncpy- copy n characters of one string to another

strdup- return pointer to new duplicate string

strlen- return number of characters in string

strchr- return pointer to first (last) occurrence of c

strrchr- return pointer to first (last) occurrence of c

strpbrk- return pointer to first occurrence in string1 of any character in string2

strspn- return length of initial segment of string1 of characters from (not from) string2

strcspn- return length of initial segment of string1 of characters from (not from) string2

strtok- return pointer of string token

strtok_r- return pointer of string token

strstr- locate first occurrence in string1 of sequence from string2

The arguments s, s1, and s2 point to strings (arrays of characters terminated by a null character). The functions strcat, strncat, strcpy, strncpy, strtok, and strtok_r alter s1. These functions do not check for overflow of the array pointed to by s1.

strcat appends a copy of string s2, including the terminating null character, to the end of string s1. strncat appends at most n characters. Each returns a pointer to the null-terminated result. The initial character of s2 overrides the null character at the end of s1.

strcmp compares its arguments and returns an integer less than, equal to, or greater than 0, based upon whether s1 is lexicographically less than, equal to, or greater than s2. strncmp makes the same comparison but looks at most n characters. Characters following a null character are not compared.

strcpy copies string s2 to s1 including the terminating null character, stopping after the null character has been copied. strncpy copies exactly n characters, 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. Each function returns s1.

strdup returns a pointer to a new string which is a duplicate of the string pointed to by s1. The space for the new string is obtained using malloc(3C). If the new string can not be created, a NULL pointer is returned.

strlen returns the number of characters in s, not including the terminating null character.

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

strpbrk returns a pointer to the first occurrence in string s1 of any character from string s2, or a NULL pointer if no character from s2 exists in s1.

strspn (or strcspn) returns the length of the initial segment of string s1 which consists entirely of characters from (not from) string s2.

strtok_r considers the string s1 to consist of a sequence of zero or more text tokens separated by spans of one or more characters from the separator string s2. The first call (with pointer s1 non-null) returns a pointer to the first character of the first token, will have written a null character into s1 immediately following the returned token and will save in the object pointed to by next information sufficient to continue tokenizing the same string in subsequent calls. To continue with the same string, s1 should be a null pointer, and the object pointed to by next should not be modified. In this way, subsequent calls will work through the string s1 until no tokens remain. The separator string s2 may be different from call to call. When no token remains in s1, a NULL pointer is returned.

strtok behaves just like strtok_r except that it remembers its own position within a single string, s1, instead of using a provided object (as is pointed to by next with strtok_r).

strstr locates the first occurrence in string s1 of the sequence of characters (excluding the terminating null character) in string s2. strstr returns a pointer to the located string, or a null pointer if the string is not found. If s2 points to a string with zero length (that is, the string ``""''), the function returns s1.

References

Notices

The reentrant version, strtok_r, is recommended for multi-threaded applications.