string(S)

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

Syntax

cc . . . -lc

#include  <string.h>

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

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

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

char *strcpy (s1, s2)
char *s1, *s2;

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

char *strdup (s1)
char *s1;

size_t strlen (s)
char *s;

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

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

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

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

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

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

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

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

Description

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

strcat appends a copy of string s2 to the end of string s1. If unsuccessful completion occurs strcat returns a null pointer. strncat appends at most n characters. Each returns a pointer to the null-terminated result. The initial character of s2 overwrites the null character at the end of s1.

strcmp compares its arguments and returns an integer less than, equal to, or greater than 0, according as s1 is lexicographically less than, equal to, or greater than s2. strncmp makes the same comparison but looks at most n characters.

strcpy copies string s2 to s1, 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 is not null-terminated if the length of s2 is n or more. Each function returns s1, or null on an unsuccessful completion. If the array pointed to by s2 is a string shorter than n characters, null characters are appended to the copy in the array pointed to by s1, until n characters in all have been written.

strchr returns a pointer to the first occurrence of character c in string s, or a null pointer if c does not occur in the string. strrchr returns a pointer to the last occurrence of character c in string s, or a null pointer if c does not occur in the string. In both routines, the null character terminating a string is considered to be part of the string.

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(S). If the new string cannot be created, null is returned.

strlen returns the number of characters 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.

strspn and strcspn return the length of the initial segment of string s1 that consists entirely of characters from (or not from in the case of strcspn) string s2.

strstr finds the first occurrence in string s1 of string s2. If s2 has zero length, a pointer to s1 is returned. If s2 is not found, a null pointer is returned. Otherwise, a pointer to the located substring in s1 is returned.

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 has 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) work through the string s1 immediately following that token. In this way subsequent calls 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.

For user convenience, all these functions are declared in the optional <string.h> header file.

Notes

strcmp and strncmp are implemented by using the most natural character comparison on the machine. Thus the sign of the value returned when one of the characters has its high-order bit set is not the same in all implementations and should not be relied upon. For XPG4 and ANSI, the sign of a nonzero value returned by strcmp or strncmp is determined by the sign of the difference between the values of the first pair of characters that differ in the objects being compared. The first pair of characters are interpreted as unsigned char.

Character movement is performed differently in different implementations. Thus overlapping moves may yield surprises.

Standards conformance

strcat, strchr, strcmp, strcpy, strcspn, strlen, strncat, strncmp, strpbrk, strspn and strtok are conformant with:

X/Open CAE Specification, System Interfaces and Headers, Issue 4, 1992 ;
ANSI X3.159-1989 Programming Language -- C ;
Intel386 Binary Compatibility Specification, Edition 2 (iBCSe2) ;
IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C Language] (ISO/IEC 9945-1) ; and NIST FIPS 151-1 .

strdup is conformant with:

X/Open CAE Specification, System Interfaces and Headers, Issue 4, 1992 .

strstr is conformant with: