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Name

Synopsis

#include <string.h>

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

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

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

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

char *strchr(const char *s, int c);

char *strrchr(const char *s, int c);

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

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

char *strdup(const char *s1);

size_t strlen(const char *s);

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

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

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

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

MT-Level

See the NOTES section of this page.

Description

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

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

strchr() 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. strrchr() returns a pointer to the last occurrence of c. The null character terminating a string is considered to be part of the string.

strcmp() 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. strncmp() makes the same comparison but looks at a maximum of n bytes. Bytes following a null byte are not compared.

strcpy() copies string src to dst including the terminating null character, stopping after the null character has been copied. strncpy() copies exactly n bytes, truncating src or adding null characters to dst if necessary. The result will not be null-terminated if the length of src is n or more. Each function returns dst.

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

strdup() returns a pointer to a new string that 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 cannot be created, a null pointer is returned.

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

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.

strstr() locates the first occurrence of the string s2 (excluding the terminating null character) in string s1. 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.

strtok() can be used to break the string pointed to by s1 into a sequence of tokens, each of which is delimited by one or more characters from the string pointed to by s2. strtok() 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 specified) returns a pointer to the first character of the first token, and will have written a null character into s1 immediately following the returned token. The function keeps track of its position in the string between separate calls, so that subsequent calls (which must be made with the first argument being a null pointer) will work through the string s1 immediately following that token. 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_r() has the same functionality as strtok() except that a pointer to a string placeholder lasts must be supplied by the caller. The lasts pointer is to keep track of the next substring in which to search for the next token.

See Also

Notes

When compiling multi-thread applications, the _REENTRANT flag must be defined on the compile line. This flag should only be used in multi-thread applications.

All of these functions assume the default locale ‘‘C.’’ For some locales, strxfrm() should be applied to the strings before they are passed to the functions.

strtok() is unsafe in multi-thread applications. strtok_r() should be used instead.

string(), strcasecmp(), strcat(), strchr(), strcmp(), strcpy(), strcspn(), strdup(), strlen(), strncasecmp(), strncat(), strncmp(), strncpy(), strpbrk(), strrchr(), strspn(), and strstr(), are MT-Safe in multi-thread applications.

Table of Contents

• Name
• Synopsis
• MT-Level
• Description
• See Also
• Notes