string
Purpose
Performs operations on strings.
Library
Standard C Library (libc.a)
Syntax
#include <string.h>
char *strcat (s1, s2) int strlen (s)
char *s1, *s2; char *s;
char *strncat (s1, s2, n) char *strchr (s, c)
char *s1, *s2; char *s, c;
int n;
char *strrchr (s, c)
int strcmp (s1, s2) char *s, c;
char *s1, *s2;
char *strpbrk (s1, s2)
int strncmp (s1, s2, n) char *s1, *s2;
char *s1, *s2;
int n; int strspn (s1, s2)
char *s1, *s2;
char *strcpy (s1, s2)
char *s1, *s2; int strcspn (s1, s2)
char *s1, *s2;
char *strncpy (s1, s2, n)
char *s1, *s2; char *strtok (s1, s2)
int n; char *s1, *s2;
Description
The string subroutines copy, compare, and append strings
in memory, and they determine such things as location,
size, and existence of strings in memory.
The parameters s1, s2 and s point to strings. A string
is an array of characters terminated by a null character.
The subroutines strcat, strncat, strcpy, and strncpy all
alter s1. They do not check for overflow of the array
pointed to by s1. All string movement is performed char-
acter by character and starts at the left. Overlapping
moves toward the left work as expected, but overlapping
moves to the right may give unexpected results. All of
these subroutines are declared in the string.h header
file.
The strcat subroutine adds a copy of the string pointed
to by the s2 parameter to the end of the string pointed
to by the s1 parameter. The strcat subroutine returns a
pointer to the null-terminated result.
The strncat subroutine copies at most n bytes of s2 to
the end of the string pointed to by the s1 parameter.
Copying stops before n bytes if a null character is
encountered in the s2 string. The strncat subroutine
returns a pointer to the null-terminated result.
The strcmp subroutine lexicographically compares the
string pointed to by the s1 parameter to the string
pointed to by the s2 parameter. The strcmp subroutine
uses native character comparison, which may be signed or
unsigned. The strcmp subroutine returns a value that is:
Less than 0 If s1 is less than s2
Equal to 0 If s1 is equal to s2
Greater than 0 If s1 is greater than s2.
The strncmp subroutine makes the same comparison as
strcmp, but it compares at most n pairs of characters.
The strcpy subroutine copies the string pointed to by the
s2 parameter to the character array pointed to by the s1
parameter. Copying stops when the null character is
copied. The strcpy subroutine returns the value of the
s1 parameter.
The strncpy subroutine copies n bytes from the string
pointed to by the s2 parameter to the character array
pointed to by the s1 parameter. If s2 is less than n
characters long, then strncpy pads s1 with trailing null
characters to fill n bytes. If s2 is n or more charac-
ters long, then only the first n characters are copied
and the result is not terminated with a null character.
The strncpy subroutine returns the value of the s1 param-
eter.
The strlen subroutine returns the number of characters in
the string pointed to by the s parameter, not including
the terminating null character.
The strchr subroutine returns a pointer to the first
occurrence of the character specified by the c parameter
in the string pointed to by the s parameter. A NULL
pointer is returned if the character does not occur in
the string. The null character that terminates a string
is considered to be part of the string.
The strrchr subroutine returns a pointer to the last
occurrence of the character specified by the c parameter
in the string pointed to by the s parameter. A NULL
pointer is returned if the character does not occur in
the string. The null character that terminates a string
is considered to be part of the string.
The strpbrk subroutine returns a pointer to the first
occurrence in the string pointed to by the s1 parameter
of any character from the string pointed to by the s2
parameter. A NULL pointer is returned if no character
matches.
The strspn subroutine returns the length of the initial
segment of the string pointed to by the s1 parameter that
consists entirely of characters from the string pointed
to by the s2 parameter.
The strcspn subroutine returns the length of the initial
segment of the string pointed to by the s1 parameter that
consists entirely of characters not from the string
pointed to by the s2 parameter.
The strtok subroutine returns a pointer to an occurrence
of a text token in the string pointed to by the s1 param-
eter. The s2 parameter specifies a set of token delim-
iters. If the s1 parameter is anything other than NULL,
then the strtok subroutine reads the string pointed to by
the s1 parameter until it finds one of the delimiter
characters specified by the s2 parameter. It then stores
a null character into the string, replacing the delim-
iter, and returns a pointer to the first character of the
text token. The strtok subroutine keeps track of its
position in the string so that subsequent calls with a
NULL s1 parameter step through the string. The delim-
iters specified by the s2 parameter can be changed for
subsequent calls to strtok. When no tokens remain in the
string pointed to by the s1 parameter, the strtok subrou-
tine returns a NULL pointer.
Related Information
In this book: " memccpy, memchr, memcmp, memcpy, memset,
bcopy," "NCstring," "NLstring," and "swab."