# <strings.h>

The <strings.h> header contains functions for manipulating strings.

> 
> 
> int bcmp(const void \*bl, const void \*b2, size\_t len); [POSIX] void
> bcopy(const void \*src, void \*dst, size\_t len); [POSIX] void
> bzero(void \*b, size\_t len); [POSIX]
> 
> 
> int ffs(int value); [POSIX]
> 
> 
> char \*index(const char \*s, int c); [POSIX]
> 
> 
> char \*rindex(const char \*s, int c); [POSIX]

## bcmp

> 
> 
> int bcmp(const void \*bl, const void \*b2, size\_t len); [POSIX]

The function compares byte string b1 against byte string b2, returning
zero if they are identical or nonzero otherwise. Both strings are
assumed to be len bytes long. Zero-length strings are always identical.
The strings can overlap.

## bcopy

> 
> 
> void bcopy(const void \*src, void \*dst, size\_t len); [POSIX]

The function copies len bytes from string src to string dst. The two
strings can overlap. If

len is zero, no bytes are copied.

## bzero

> 
> 
> void bzero(void \*b, size\_t len); [POSIX]

The function writes len zero bytes to the string b. If len is zero,
bzero does nothing.

## ffs

int ffs(int value); [POSIX]

The function finds the first bit set in value and returns the index of
that bit. Bits are numbered starting from 1, starting at the right-most
bit. A return value of 0 means that the argument was zero.

## index

> 
> 
> char \*index(const char \*s, int c); [POSIX]

The index function locates the first character matching c (converted to
a char) in the NULL- terminated string s. A pointer to the character is
returned if it is found; otherwise NULL is returned. If c is ‘\0’,
index locates the terminating ‘\0’.

## rindex

> 
> 
> char \*rindex(const char \*s, int c); [POSIX]

The function locates the last character matching c (converted to a char)
in the NULL- terminated string s. A pointer to the character is returned
if it is found; otherwise NULL is returned. If c is ‘\0’, rindex
locates the terminating ‘\0’.

Last Published: Oct 06, 2026

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