string(3C)string(3C)NAME
string: strcat, strdup, strncat, strcmp, strncmp, strcpy, strncpy,
strlen, strchr, strrchr, strpbrk, strspn, strcspn, strtok, strstr
strcasecmp, strncasecmp, index, rindex, strtok_r - 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);
int strcasecmp (const char *s1, const char *s2);
int strncasecmp (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 *strtok_r (char *s1, const char *s2, char **lasts);
char *strstr (const char *s1, const char *s2);
#include <strings.h>
char *index (const char *s, int c);
char *rindex (const char *s, int c);
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string(3C)string(3C)DESCRIPTION
The arguments s, s1, and s2 point to strings (arrays of characters
terminated by a null character). The functions strcat, strncat, strcpy,
strncpy, strtok_r, and strtok, all alter s1. These functions do not
check for overflow of the array pointed to by s1, or for overlap between
s1 and s2. If overflow of s1 occurs, or copying takes place when s1 and
s2 overlap, the behavior is undefined.
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. strcasecmp and strncasecmp are case-insensitive versions
of strcmp and strncmp, respectively. Case-insensitive comparison is
implemented by converting upper-case ASCII characters to lower-case
before comparison. Thus strcasecmp and strncasecmp only give meaningful
results for the "C" locale (7 bit ASCII).
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 (ie. if the length of n is greater than the length of s2 ).
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.
index (rindex) are included as duplicates of strchr (strrchr) for
compatibility (see Notes).
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.
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string(3C)string(3C)
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. Note that a string consisting entirely of non-
separator characters is considered a single token. For example, if the
initial call to strtok is made with s1 pointing to a string consisting
entirely of non-separator characters, then the return value from strtok
will be the value of s1 passed to strtok.
strtok_r is a reentrant version of strtok. The current location in the
string is kept track of in lasts. On the first call to strtok_r, lasts
should be a pointer to a NULL pointer. It is kept updated on each
successive call to strtok_r to point into s1 directly after the null
character. lasts must not be changed between calls to strtok_r. The
feature test macro _SGI_REENTRANT_FUNCTIONS should be defined to make
this function visible.
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 (i.e., the
string ""), the function returns s1.
SEE ALSOmalloc(3C), memory(3C), setlocale(3C), strcoll(3C), strerror(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.
Declarations for index and rindex are specifically omitted from
<string.h> due to possible naming conflicts. Instead, they are declared
in <strings.h>.
The index, rindex, strcasecmp, strncasecmp routines are from the 4.3BSD
or 4.3BSD-tahoe standard C library.
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