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# <string.h>: Strings

## Detailed Description

     #include <string.h>

The string functions perform string operations on NULL terminated strings.

Note:
  If the strings you are working on resident in program space (flash), you will need to use the string functions described in <avr/pgmspace.h>: Program Space Utilities.

## Defines
#define | _FFS(x)
## Functions
int | ffs (int __val)
int | ffsl (long __val)
int | ffsll (long long __val)
void * | memccpy (void *, const void *, int, size_t)
void * | memchr (const void *, int, size_t) __ATTR_PURE__
int | memcmp (const void *, const void *, size_t) __ATTR_PURE__
void * | memcpy (void *, const void *, size_t)
void * | memmem (const void *, size_t, const void *, size_t) __ATTR_PURE__
void * | memmove (void *, const void *, size_t)
void * | memrchr (const void *, int, size_t) __ATTR_PURE__
void * | memset (void *, int, size_t)
int | strcasecmp (const char *, const char *) __ATTR_PURE__
char * | strcasestr (const char *, const char *) __ATTR_PURE__
char * | strcat (char *, const char *)
char * | strchr (const char *, int) __ATTR_PURE__
char * | strchrnul (const char *, int) __ATTR_PURE__
int | strcmp (const char *, const char *) __ATTR_PURE__
char * | strcpy (char *, const char *)
size_t | strcspn (const char *__s, const char *__reject) __ATTR_PURE__
char * | strdup (const char *s1)
size_t | strlcat (char *, const char *, size_t)
size_t | strlcpy (char *, const char *, size_t)
size_t | strlen (const char *) __ATTR_PURE__
char * | strlwr (char *)
int | strncasecmp (const char *, const char *, size_t) __ATTR_PURE__
char * | strncat (char *, const char *, size_t)
int | strncmp (const char *, const char *, size_t) __ATTR_PURE__
char * | strncpy (char *, const char *, size_t)
size_t | strnlen (const char *, size_t) __ATTR_PURE__
char * | strpbrk (const char *__s, const char *__accept) __ATTR_PURE__
char * | strrchr (const char *, int) __ATTR_PURE__
char * | strrev (char *)
char * | strsep (char **, const char *)
size_t | strspn (const char *__s, const char *__accept) __ATTR_PURE__
char * | strstr (const char *, const char *) __ATTR_PURE__
char * | strtok (char *, const char *)
char * | strtok_r (char *, const char *, char **)
char * | strupr (char *)

## Define Documentation

#define _FFS | ( | x |  | ) |

This macro finds the first (least significant) bit set in the input value.

This macro is very similar to the function ffs() except that it evaluates its argument at compile-time, so it should only be applied to compile-time constant expressions where it will reduce to a constant itself. Application of this macro to expressions that are not constant at compile-time is not recommended, and might result in a huge amount of code generated.

Returns:
  The _FFS() macro returns the position of the first (least significant) bit set in the word val, or 0 if no bits are set. The least significant bit is position 1.

## Function Documentation

int ffs | ( | int | val | ) |

This function finds the first (least significant) bit set in the input value.

Returns:
  The ffs() function returns the position of the first (least significant) bit set in the word val, or 0 if no bits are set. The least significant bit is position 1.

Note:
  For expressions that are constant at compile time, consider using the _FFS macro instead.

int ffsl | ( | long | __val | ) |

Same as ffs(), for an argument of type long.

int ffsll | ( | long long | __val | ) |

Same as ffs(), for an argument of type long long.

void * memccpy | ( | void * | dest,
|  | const void * | src,
|  | int | val,
|  | size_t | len |
| ) |  |  |

Copy memory area.

The memccpy() function copies no more than len bytes from memory area src to memory area dest, stopping when the character val is found.

Returns:
  The memccpy() function returns a pointer to the next character in dest after val, or NULL if val was not found in the first len characters of src.

void * memchr | ( | const void * | src,
|  | int | val,
|  | size_t | len |
| ) |  |  |

Scan memory for a character.

The memchr() function scans the first len bytes of the memory area pointed to by src for the character val. The first byte to match val (interpreted as an unsigned character) stops the operation.

Returns:
  The memchr() function returns a pointer to the matching byte or NULL if the character does not occur in the given memory area.

int memcmp | ( | const void * | s1,
|  | const void * | s2,
|  | size_t | len |
| ) |  |  |

Compare memory areas.

The memcmp() function compares the first len bytes of the memory areas s1 and s2. The comparision is performed using unsigned char operations.

Returns:
  The memcmp() function returns an integer less than, equal to, or greater than zero if the first len bytes of s1 is found, respectively, to be less than, to match, or be greater than the first len bytes of s2.

Note:
  Be sure to store the result in a 16 bit variable since you may get incorrect results if you use an unsigned char or char due to truncation.

Warning:
  This function is not -mint8 compatible, although if you only care about testing for equality, this function should be safe to use.

void * memcpy | ( | void * | dest,
|  | const void * | src,
|  | size_t | len |
| ) |  |  |

Copy a memory area.

The memcpy() function copies len bytes from memory area src to memory area dest. The memory areas may not overlap. Use memmove() if the memory areas do overlap.

Returns:
  The memcpy() function returns a pointer to dest.

void * memmem | ( | const void * | s1,
|  | size_t | len1,
|  | const void * | s2,
|  | size_t | len2 |
| ) |  |  |

The memmem() function finds the start of the first occurrence of the substring `s2` of length `len2` in the memory area `s1` of length `len1`.

Returns:
  The memmem() function returns a pointer to the beginning of the substring, or `NULL` if the substring is not found. If `len2` is zero, the function returns `s1`.

void * memmove | ( | void * | dest,
|  | const void * | src,
|  | size_t | len |
| ) |  |  |

Copy memory area.

The memmove() function copies len bytes from memory area src to memory area dest. The memory areas may overlap.

Returns:
  The memmove() function returns a pointer to dest.

void * memrchr | ( | const void * | src,
|  | int | val,
|  | size_t | len |
| ) |  |  |

The memrchr() function is like the memchr() function, except that it searches backwards from the end of the `len` bytes pointed to by `src` instead of forwards from the front. (Glibc, GNU extension.)

Returns:
  The memrchr() function returns a pointer to the matching byte or `NULL` if the character does not occur in the given memory area.

void * memset | ( | void * | dest,
|  | int | val,
|  | size_t | len |
| ) |  |  |

Fill memory with a constant byte.

The memset() function fills the first len bytes of the memory area pointed to by dest with the constant byte val.

Returns:
  The memset() function returns a pointer to the memory area dest.

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

Compare two strings ignoring case.

The strcasecmp() function compares the two strings `s1` and `s2`, ignoring the case of the characters.

Returns:
  The strcasecmp() function returns an integer less than, equal to, or greater than zero if `s1` is found, respectively, to be less than, to match, or be greater than `s2`. A consequence of the ordering used by strcasecmp() is that if `s1` is an initial substring of `s2`, then `s1` is considered to be "less than" `s2`.

char * strcasestr | ( | const char * | s1,
|  | const char * | s2 |
| ) |  |  |

The strcasestr() function finds the first occurrence of the substring `s2` in the string `s1`. This is like strstr(), except that it ignores case of alphabetic symbols in searching for the substring. (Glibc, GNU extension.)

Returns:
  The strcasestr() function returns a pointer to the beginning of the substring, or `NULL` if the substring is not found. If `s2` points to a string of zero length, the function returns `s1`.

char * strcat | ( | char * | dest,
|  | const char * | src |
| ) |  |  |

Concatenate two strings.

The strcat() function appends the src string to the dest string overwriting the '\0' character at the end of dest, and then adds a terminating '\0' character. The strings may not overlap, and the dest string must have enough space for the result.

Returns:
  The strcat() function returns a pointer to the resulting string dest.

char * strchr | ( | const char * | src,
|  | int | val |
| ) |  |  |

Locate character in string.

The strchr() function returns a pointer to the first occurrence of the character `val` in the string `src`.

Here "character" means "byte" - these functions do not work with wide or multi-byte characters.

Returns:
  The strchr() function returns a pointer to the matched character or `NULL` if the character is not found.

char * strchrnul | ( | const char * | s,
|  | int | c |
| ) |  |  |

The strchrnul() function is like strchr() except that if `c` is not found in `s`, then it returns a pointer to the null byte at the end of `s`, rather than `NULL`. (Glibc, GNU extension.)

Returns:
  The strchrnul() function returns a pointer to the matched character, or a pointer to the null byte at the end of `s` (i.e., `s+strlen`(s)) if the character is not found.

int strcmp | ( | const char * | s1,
|  | const char * | s2 |
| ) |  |  |

Compare two strings.

The strcmp() function compares the two strings `s1` and `s2`.

Returns:
  The strcmp() function returns an integer less than, equal to, or greater than zero if `s1` is found, respectively, to be less than, to match, or be greater than `s2`. A consequence of the ordering used by strcmp() is that if `s1` is an initial substring of `s2`, then `s1` is considered to be "less than" `s2`.

char * strcpy | ( | char * | dest,
|  | const char * | src |
| ) |  |  |

Copy a string.

The strcpy() function copies the string pointed to by src (including the terminating '\0' character) to the array pointed to by dest. The strings may not overlap, and the destination string dest must be large enough to receive the copy.

Returns:
  The strcpy() function returns a pointer to the destination string dest.

Note:
  If the destination string of a strcpy() is not large enough (that is, if the programmer was stupid/lazy, and failed to check the size before copying) then anything might happen. Overflowing fixed length strings is a favourite cracker technique.

size_t strcspn | ( | const char * | s,
|  | const char * | reject |
| ) |  |  |

The strcspn() function calculates the length of the initial segment of `s` which consists entirely of characters not in `reject`.

Returns:
  The strcspn() function returns the number of characters in the initial segment of `s` which are not in the string `reject`. The terminating zero is not considered as a part of string.

char * strdup | ( | const char * | s1 | ) |

Duplicate a string.

The strdup() function allocates memory and copies into it the string addressed by s1, including the terminating null character.

Warning:
  The strdup() function calls malloc() to allocate the memory for the duplicated string! The user is responsible for freeing the memory by calling free().

Returns:
  The strdup() function returns a pointer to the resulting string dest. If malloc() cannot allocate enough storage for the string, strdup() will return NULL.

Warning:
  Be sure to check the return value of the strdup() function to make sure that the function has succeeded in allocating the memory!

size_t strlcat | ( | char * | dst,
|  | const char * | src,
|  | size_t | siz |
| ) |  |  |

Concatenate two strings.

Appends src to string dst of size siz (unlike strncat(), siz is the full size of dst, not space left). At most siz-1 characters will be copied. Always NULL terminates (unless siz <= strlen(dst)).

Returns:
  The strlcat() function returns strlen(src) + MIN(siz, strlen(initial dst)). If retval >= siz, truncation occurred.

size_t strlcpy | ( | char * | dst,
|  | const char * | src,
|  | size_t | siz |
| ) |  |  |

Copy a string.

Copy src to string dst of size siz. At most siz-1 characters will be copied. Always NULL terminates (unless siz == 0).

Returns:
  The strlcpy() function returns strlen(src). If retval >= siz, truncation occurred.

size_t strlen | ( | const char * | src | ) |

Calculate the length of a string.

The strlen() function calculates the length of the string src, not including the terminating '\0' character.

Returns:
  The strlen() function returns the number of characters in src.

char * strlwr | ( | char * | s | ) |

Convert a string to lower case.

The strlwr() function will convert a string to lower case. Only the upper case alphabetic characters [A .. Z] are converted. Non-alphabetic characters will not be changed.

Returns:
  The strlwr() function returns a pointer to the converted string.

int strncasecmp | ( | const char * | s1,
|  | const char * | s2,
|  | size_t | len |
| ) |  |  |

Compare two strings ignoring case.

The strncasecmp() function is similar to strcasecmp(), except it only compares the first `len` characters of `s1`.

Returns:
  The strncasecmp() function returns an integer less than, equal to, or greater than zero if `s1` (or the first `len` bytes thereof) is found, respectively, to be less than, to match, or be greater than `s2`. A consequence of the ordering used by strncasecmp() is that if `s1` is an initial substring of `s2`, then `s1` is considered to be "less than" `s2`.

char * strncat | ( | char * | dest,
|  | const char * | src,
|  | size_t | len |
| ) |  |  |

Concatenate two strings.

The strncat() function is similar to strcat(), except that only the first n characters of src are appended to dest.

Returns:
  The strncat() function returns a pointer to the resulting string dest.

int strncmp | ( | const char * | s1,
|  | const char * | s2,
|  | size_t | len |
| ) |  |  |

Compare two strings.

The strncmp() function is similar to strcmp(), except it only compares the first (at most) n characters of s1 and s2.

Returns:
  The strncmp() function returns an integer less than, equal to, or greater than zero if s1 (or the first n bytes thereof) is found, respectively, to be less than, to match, or be greater than s2.

char * strncpy | ( | char * | dest,
|  | const char * | src,
|  | size_t | len |
| ) |  |  |

Copy a string.

The strncpy() function is similar to strcpy(), except that not more than n bytes of src are copied. Thus, if there is no null byte among the first n bytes of src, the result will not be null-terminated.

In the case where the length of src is less than that of n, the remainder of dest will be padded with nulls.

Returns:
  The strncpy() function returns a pointer to the destination string dest.

size_t strnlen | ( | const char * | src,
|  | size_t | len |
| ) |  |  |

Determine the length of a fixed-size string.

The strnlen function returns the number of characters in the string pointed to by src, not including the terminating '\0' character, but at most len. In doing this, strnlen looks only at the first len characters at src and never beyond src+len.

Returns:
  The strnlen function returns strlen(src), if that is less than len, or len if there is no '\0' character among the first len characters pointed to by src.

char * strpbrk | ( | const char * | s,
|  | const char * | accept |
| ) |  |  |

The strpbrk() function locates the first occurrence in the string `s` of any of the characters in the string `accept`.

Returns:
  The strpbrk() function returns a pointer to the character in `s` that matches one of the characters in `accept`, or `NULL` if no such character is found. The terminating zero is not considered as a part of string: if one or both args are empty, the result will `NULL`.

char * strrchr | ( | const char * | src,
|  | int | val |
| ) |  |  |

Locate character in string.

The strrchr() function returns a pointer to the last occurrence of the character val in the string src.

Here "character" means "byte" - these functions do not work with wide or multi-byte characters.

Returns:
  The strrchr() function returns a pointer to the matched character or NULL if the character is not found.

char * strrev | ( | char * | s | ) |

Reverse a string.

The strrev() function reverses the order of the string.

Returns:
  The strrev() function returns a pointer to the beginning of the reversed string.

char * strsep | ( | char ** | sp,
|  | const char * | delim |
| ) |  |  |

Parse a string into tokens.

The strsep() function locates, in the string referenced by `*sp`, the first occurrence of any character in the string `delim` (or the terminating '\0' character) and replaces it with a '\0'. The location of the next character after the delimiter character (or `NULL`, if the end of the string was reached) is stored in `*sp`. An ``empty'' field, i.e. one caused by two adjacent delimiter characters, can be detected by comparing the location referenced by the pointer returned in `*sp` to '\0'.

Returns:
  The strsep() function returns a pointer to the original value of `*sp`. If `*sp` is initially `NULL`, strsep() returns `NULL`.

size_t strspn | ( | const char * | s,
|  | const char * | accept |
| ) |  |  |

The strspn() function calculates the length of the initial segment of `s` which consists entirely of characters in `accept`.

Returns:
  The strspn() function returns the number of characters in the initial segment of `s` which consist only of characters from `accept`. The terminating zero is not considered as a part of string.

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

Locate a substring.

The strstr() function finds the first occurrence of the substring `s2` in the string `s1`. The terminating '\0' characters are not compared.

Returns:
  The strstr() function returns a pointer to the beginning of the substring, or `NULL` if the substring is not found. If `s2` points to a string of zero length, the function returns `s1`.

char * strtok | ( | char * | s,
|  | const char * | delim |
| ) |  |  |

Parses the string s into tokens.

strtok parses the string s into tokens. The first call to strtok should have s as its first argument. Subsequent calls should have the first argument set to NULL. If a token ends with a delimiter, this delimiting character is overwritten with a '\0' and a pointer to the next character is saved for the next call to strtok. The delimiter string delim may be different for each call.

Returns:
  The strtok() function returns a pointer to the next token or NULL when no more tokens are found.

Note:
  strtok() is NOT reentrant. For a reentrant version of this function see `strtok_r()`.

char * strtok_r | ( | char * | string,
|  | const char * | delim,
|  | char ** | last |
| ) |  |  |

Parses string into tokens.

strtok_r parses string into tokens. The first call to strtok_r should have string as its first argument. Subsequent calls should have the first argument set to NULL. If a token ends with a delimiter, this delimiting character is overwritten with a '\0' and a pointer to the next character is saved for the next call to strtok_r. The delimiter string delim may be different for each call. last is a user allocated char* pointer. It must be the same while parsing the same string. strtok_r is a reentrant version of strtok().

Returns:
  The strtok_r() function returns a pointer to the next token or NULL when no more tokens are found.

char * strupr | ( | char * | s | ) |

Convert a string to upper case.

The strupr() function will convert a string to upper case. Only the lower case alphabetic characters [a .. z] are converted. Non-alphabetic characters will not be changed.

Returns:
  The strupr() function returns a pointer to the converted string. The pointer is the same as that passed in since the operation is perform in place.

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