.\" Copyright (c) 1980 Regents of the University of California.

.\" All rights reserved. The Berkeley software License Agreement

.\" specifies the terms and conditions for redistribution.

.\"

.\" @(#)string.3 6.1 (Berkeley) 5/15/85

.\"

.TH STRING 3 "May 15, 1985"

.UC 4

.SH NAME

string, strcat, strncat, strcmp, strncmp, strcpy, strncpy, strlen, strchr, strrchr, strerror, memcmp, memcpy, memmove, memchr, memset, index, rindex \- string operations

.SH SYNOPSIS

.nf

.ft B

#include <string.h>

char *strcat(char *\fIs1\fP, const char *\fIs2\fP)

char *strncat(char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)

int strcmp(const char *\fIs1\fP, const char *\fIs2\fP)

int strncmp(const char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)

char *strcpy(char *\fIs1\fP, const char *\fIs2\fP)

char *strncpy(char *\fIs1\fP, const char *\fIs2\fP, size_t \fIn\fP)

size_t strlen(const char *\fIs\fP)

char *strchr(const char *\fIs\fP, int \fIc\fP)

char *strrchr(const char *\fIs\fP, int \fIc\fP)

char *strerror(int \fIerrnum\fP)

int memcmp(const void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)

void *memcpy(void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)

void *memmove(void *\fIs1\fP, const void *\fIs2\fP, size_t \fIn\fP)

void *memchr(const void *\fIs\fP, int \fIc\fP, size_t \fIn\fP)

void *memset(void *\fIs\fP, int \fIc\fP, size_t \fIn\fP)

char *index(const char *\fIs\fP, int \fIc\fP)

char *rindex(const char *\fIs\fP, int \fIc\fP)

.ft R

.fi

.SH DESCRIPTION

These functions operate on null-terminated strings.

They do not check for overflow of any receiving string.

.PP

.B Strcat

appends a copy of string

.I s2

to the end of string

.IR s1 .

.B Strncat

copies at most

.I n

characters. Both return a pointer to the null-terminated result.

.PP

.B Strcmp

compares its arguments and returns an integer

greater than, equal to, or less than 0, according as

.I s1

is lexicographically greater than, equal to, or less than

.IR s2 .

.B Strncmp

makes the same comparison but looks at at most

.I n

characters.

.PP

.B Strcpy

copies string

.I s2

to

.IR s1 ,

stopping after the null character has been moved.

.B Strncpy

copies exactly

.I n

characters, truncating or null-padding

.I s2;

the target may not be null-terminated if the length of

.I s2

is

.I n

or more. Both return

.IR s1 .

.PP

.B Strlen

returns the number of non-null characters in

.IR s .

.PP

.B Strchr

.RB ( strrchr )

returns a pointer to the first (last) occurrence of character

.I c

in string

.I s,

or null if

.I c

does not occur in the string.

.PP

.B Strerror

returns the error string for the system call error

.IR errnum .

See

.BR intro (2).

.PP

.B Memcmp

is like

.B strcmp

except that the strings are memory blocks of length

.IR n .

Null characters are treated as ordinary characters.

.PP

.B Memcpy

copies

.I n

bytes from the location pointed to by

.I s2

to

.IR s1 .

.B Memmove

is like memcpy, except that it can handle overlap between the two strings.

Both functions return

.IR s1 .

.PP

.B Memchr

returns a pointer to the first occurrence of character

.I c

in string

.I s,

or null if

.I c

does not occur in the string.

.PP

.B Memset

sets

.I n

bytes to

.I c

starting at location

.IR s .

It returns

.IR s .

.PP

.B Index

and

.B rindex

are obsolete versions of

.B strchr

and

.BR strrchr .

New code should avoid using them.

.SH NOTES

Characters are compared as

.BR "unsigned char" ,

whether

.B char

itself is signed or not.