NAME

string: strcat, strdup, strncat, strcmp, strncmp, strcpy, strncpy, strlen, strchr, strrchr, strpbrk, strspn, strcspn, strtok, strstr − string operations

SYNOPSIS

#include <string.h>

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

char ∗strdup (const char ∗s1);

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);

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

DESCRIPTION

The arguments s, s1, and s2 point to strings (arrays of characters terminated by a null character).  The functions strcat, strncat, strcpy, strncpy, and strtok.  all 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 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 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 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. 

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. 

SEE ALSO

malloc(3C), setlocale(3C), strxfrm(3C)

NOTES

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. 

  —  C Development Set