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memchr function | Searches for a byte |
const void* memchr (const void* mem, int c, size_t n) void* memchr ( void* mem, int c, size_t n) |
The memchr function searches the memory that mem points to, of size n bytes, for the byte whose value is c (converted to unsigned char ). The return value is a pointer into the mem array to the first occurrence of c , or a null pointer if c is not present in the first n bytes of mem .
strchr function, find in <algorithm> , wmemchr in <cwchar>
memcmp function | Compares memory |
int memcmp (const void* s1, const void* s2, size_t n) |
The memcmp function compares the first n bytes of s1 and s2 as arrays of unsigned char . If all n bytes are equal, the return value is . Otherwise, the return value is positive if s1 is greater than s2 or negative if s1 is less than s2 .
strcmp function, strncmp function, equal in <algorithm >, lexicographical_compare in <algorithm> , mismatch in <algorithm> , wmemcmp in <cwchar>
memcpy function | Copies memory |
void* memcpy (void* dst, const void* src, size_t n) |
The memcpy function copies n bytes from src to dst . If src and dst overlap, the results are undefined. The return value is dst .
If you copy the memory that contains any non-POD objects, the results are undefined. See Chapter 6 for more information about POD objects.
memmove function, strcpy function, strncpy function, copy in <algorithm> , wmemcpy in <cwchar> , Chapter 6
memmove function | Copies possibly overlapping memory |
void* memmove (void* dst, const void* src, size_t n) |
The memmove function copies n bytes from src to dst . The memory regions can overlap. The return value is dst .
If you copy the memory that contains any non-POD objects, the results are undefined. See Chapter 6 for more information about POD objects.
memcpy function, strcpy function, strncpy function, copy in <algorithm >, copy_backward in <algorithm> , wmemmove in <cwchar> , Chapter 6
memset function | Fills memory with a byte |
void* memset (void* s, int c, size_t n) |
The memset function fills the array s with n copies of c (converted to unsigned char ). The return value is s .
memcpy function, fill_n in <algorithm> , wmemset in <cwchar>
NULL macro | NULL pointer constant |
#define NULL . . . |
The NULL macro expands to a null pointer constant. See <cstddef> for more information.
NULL in <cstddef>
size_t type | Size type |
typedef . . . size_t |
The size_t type is the type of the result of the sizeof operator. It is an unsigned integral type. The exact type is implementation-defined.
size_t in <cstddef>
strcat function | Concatenates strings |
char* strcat (char* dst, const char* src) |
The strcat function concatenates src onto the end of dst , overwriting the null byte that ends dst . The src and dst arrays cannot overlap. The caller must ensure that dst points to a region of memory that is large enough to hold the concatenated result, including its null terminator.
strcpy function, strncat function, wcscat in <cwchar>
strchr function | Searches a string for a character |
const char* strchr (const char* s, int c) char* strchr ( char* s, int c) |
The strchr function returns a pointer to the first occurrence of c (converted to unsigned char ) in the null-terminated string s . If c does not appear in s , a null pointer is returned.
memchr function, strcspn function, strpbrk function, strrchr function, strspn function, wcschr in <cwchar>
strcmp function | Compares strings |
int strcmp (const char* s1, const char* s2) |
The strcmp function compares two null-terminated strings as arrays of unsigned char . If the strings are equal, the return value is . Otherwise, the return value is positive if s1 is greater than s2 or negative if s1 is less than s2 . If one string is a prefix of the other, the longer string is greater than the shorter string.
memcmp function, strncmp function, wcscmp in <cwchar>
strcoll function | Compares strings using locale's collation order |
int strcoll (const char* s1, const char* s2) |
The strcoll function compares two null-terminated strings, interpreting the strings according to the LC_COLLATE (defined in <clocale> ) category of the current C locale. The return value is the same as that of strcmp .
strcmp function, wcscoll in <cwchar >, collate in <locale> , <clocale>
strcpy function | Copies a string |
char* strcpy (char* dst, const char* src) |
The strcpy function copies the null-terminated string src to dst . The caller must ensure that dst points to a region of memory that is large enough to hold the entire src string plus its null terminator. The return value is dst .
memcpy function, strncpy function, wcscpy in <cwchar>
strcspn function | Counts initial characters not in a span set |
size_t strcspn (const char* str, const char* spanset) |
The strcspn function returns the number of characters at the start of str that are not in the string spanset . Thus, the c in its name means complement, that is, strcspn counts characters that are in the complement of the span set.
strchr function, strpbrk function, strspn function, strstr function, wcscspn in <cwchar>
strerror function | Retrieves error message text |
char* strerror (int errnum) |
The strerror function returns a pointer to an error message string that corresponds to the error number errnum . The message is the same as that printed by the perror function.
A program must not modify the array returned by strerror , and subsequent calls to strerror can overwrite the array.
perror in <cstdio> , <cerrno>
strlen function | Computes length of a string |
size_t strlen (const char* s) |
The strlen function returns the length of the null-terminated string s , that is, the number of bytes that come before the null byte at the end of the string.
wcslen in <cwchar>
strncat function | Concatenates strings |
char* strncat (char* dst, const char* src, size_t n) |
The strncat function concatenates src onto the end of dst , overwriting the null byte at the end of dst . At most, n characters are copied from src . A terminating null character is always appended to the end of dst . The caller must ensure that dst points to a region of memory that is large enough to hold the concatenated result, including the null terminator. The return value is dst .
strcat function, wcsncat in <cwchar>
strncmp function | Compares strings |
int strncmp (const char* s1, const char* s2, size_t n) |
The strncmp function compares at most n characters of two null-terminated strings as arrays of unsigned char . If the strings are equal, the return value is . Otherwise, the return value is positive if s1 is greater than s2 or negative if s1 is less than s2 . If one string is a prefix of the other, the longer string is greater than the shorter string.
memcmp function, strcmp function, wcsncmp in <cwchar>
strncpy function | Copies a string |
char* strncpy (char* dst, const char* src, size_t n) |
The strncpy function copies at most n characters from the null-terminated string src to dst . If src is shorter than dst , null characters are appended to the end so that exactly n characters are always written to dst .
The return value is dst .
memcpy function, strcpy function, wcsncpy in <cwchar>
strpbrk function | Locates a character in a span set |
const char* strpbrk (const char* str, const char* spanset) char* strpbrk ( char* str, const char* spanset) |
The strpbrk function searches str for any of the characters in spanset and returns a pointer to the first occurrence of such a character. If none of the characters in spanset appear in str , strpbrk returns a null pointer.
strchr function, strcspn function, strspn function, wcspbrk in <cwchar>
strrchr function | Locates rightmost occurrence of a character |
const char* strrchr (const char* str, int c) char* strrchr ( char* str, int c) |
The strrchr function returns a pointer to the last (rightmost) occurrence of c (converted to unsigned char ) in the null-terminated string s . If c does not appear in s , NULL is returned.
memchr function, strchr function, wcsrchr in <cwchar>
strspn function | Counts characters in a span set |
size_t strspn (const char* str, const char* spanset) |
The strspn function returns the number of characters at the start of str that are in the string spanset .
strchr function, strcspn function, strpbrk function, wcsspn in <cwchar>
strstr function | Finds a substring |
const char* strstr (const char* str, const char* substr) char* strstr ( char* str, const char* substr) |
The strstr function returns the address in str of the first occurrence of substr or a null pointer if substr does not appear in str .
strchr function, wcsstr in <cwchar>
strtok function | Tokenizes a string |
char* strtok (char* str, const char* delimset) |
The strtok function splits str into separate tokens, separated by one or more characters from delimset . The contents of str are modified when each token is found.
To parse a string str , you must call strtok multiple times. The first time, pass str as the first parameter to strtok ; for the second and subsequent calls, pass a null pointer. Because strtok saves str , only one series of strtok calls can be active at a time. Each call to strtok can use a different delimset .
The strtok function skips over initial delimiters, searching str for the first character that is not in delimset . If it reaches the end of the string without finding any token characters, it returns a null pointer. Otherwise, it saves a pointer to the first non- delimiter character as the start of the token. It then searches for the next delimiter character, which ends the token. It changes the delimiter character to a null character and returns a pointer to the start of the token. When strtok is called with a null pointer as the first parameter, it starts searching for the next token at the point where the previous search ended.
strcspn function, strpbrk function, strspn function, wcstok in <cwchar>
strxfrm function | Transforms a string for collation |
size_t strxfrm (char* dst, const char* src, size_t n) |
The strxfrm function transforms the src string by converting each character to its collation order equivalent. The equivalent is copied into dst . Thus, after transforming two different strings with strxfrm , the transformed strings can be compared by calling strcmp to obtain the same result as calling strcoll on the original strings.
No more than n bytes are stored in dst , including the trailing null character. If n is , dst can be null.
The return value is the number of transformed characters written to dst .
strcmp function, strcoll function, wcsxfrm in <cwchar> , collate in <locale> , <clocale>