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.TH STRCAT 2

.SH NAME

strcat, strncat, strcmp, strncmp, cistrcmp, cistrncmp, strcpy, strncpy, strecpy, strlen, strchr, strrchr, strpbrk, strspn, strcspn, strtok, strdup, strstr, cistrstr \- string operations

.SH SYNOPSIS

.B #include <u.h>

.br

.B #include <libc.h>

.PP

.ta \w'\fLchar* \fP'u

.B

char*	strcat(char *s1, char *s2)

.PP

.B

char*	strncat(char *s1, char *s2, long n)

.PP

.B

int	strcmp(char *s1, char *s2)

.PP

.B

int	strncmp(char *s1, char *s2, long n)

.PP

.B

int	cistrcmp(char *s1, char *s2)

.PP

.B

int	cistrncmp(char *s1, char *s2, long n)

.PP

.B

char*	strcpy(char *s1, char *s2)

.PP

.B

char*	strecpy(char *s1, char *es1, char *s2)

.PP

.B

char*	strncpy(char *s1, char *s2, long n)

.PP

.B

long	strlen(char *s)

.PP

.B

char*	strchr(char *s, char c)

.PP

.B

char*	strrchr(char *s, char c)

.PP

.B

char*	strpbrk(char *s1, char *s2)

.PP

.B

long	strspn(char *s1, char *s2)

.PP

.B

long	strcspn(char *s1, char *s2)

.PP

.B

char*	strtok(char *s1, char *s2)

.PP

.B

char*	strdup(char *s)

.PP

.B

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

.PP

.B

char*	cistrstr(char *s1, char *s2)

.SH DESCRIPTION

The arguments

.I s1, s2

and

.I s

point to null-terminated strings.

The functions

.IR strcat ,

.IR strncat ,

.IR strcpy ,

.IR strecpy ,

and

.I strncpy

all alter

.IR s1 .

.I Strcat

and

.I strcpy

do not check for overflow of

the array pointed to by

.IR s1 .

.PP

.I Strcat

appends a copy of string

.I s2

to the end of string

.IR s1 .

.I Strncat

appends at most

.I n

bytes.

Each returns a pointer to the null-terminated result.

.PP

.I Strcmp

compares its arguments and returns an integer

less than, equal to, or greater than 0,

according as

.I s1

is lexicographically less than, equal to, or

greater than

.IR s2 .

.I Strncmp

makes the same comparison but examines at most

.I n

bytes.

.I Cistrcmp

and

.I cistrncmp

ignore ASCII case distinctions when comparing strings.

The comparisons are made with unsigned bytes.

.PP

.I Strcpy

copies string

.I s2

to

.IR s1 ,

stopping after the null byte has been copied.

.I Strncpy

copies exactly

.I n

bytes,

truncating

.I s2

or adding

null bytes to

.I s1

if necessary.

The result will not be null-terminated if the length

of

.I s2

is

.I n

or more.

Each function returns

.IR s1 .

.PP

.I Strecpy

copies bytes until a null byte has been copied, but writes no bytes beyond

.IR es1 .

If any bytes are copied,

.I s1

is terminated by a null byte, and a pointer to that byte is returned.

Otherwise, the original

.I s1

is returned.

.PP

.I Strlen

returns the number of bytes in

.IR s ,

not including the terminating null byte.

.PP

.I Strchr

.RI ( strrchr )

returns a pointer to the first (last)

occurrence of byte

.I c

in string

.IR s ,

or

.L 0

if

.I c

does not occur in the string.

The null byte terminating a string is considered to

be part of the string.

.PP

.I Strpbrk

returns a pointer to the first occurrence in string

.I s1

of any byte from string

.IR s2 ,

.L 0

if no byte from

.I s2

exists in

.IR s1 .

.PP

.I Strspn

.RI ( strcspn )

returns the length of the initial segment of string

.I s1

which consists entirely of bytes from (not from) string

.IR s2 .

.PP

.I Strtok

considers the string

.I s1

to consist of a sequence of zero or more text tokens separated

by spans of one or more bytes from the separator string

.IR s2 .

The first call, with pointer

.I s1

specified, returns a pointer to the first byte of the first

token, and will have written a

null byte into

.I s1

immediately following the returned token.

The function

keeps track of its position in the string

between separate calls; subsequent calls,

signified by

.I s1

being

.LR 0 ,

will work through the string

.I s1

immediately following that token.

The separator string

.I s2

may be different from call to call.

When no token remains in

.IR s1 ,

.L 0

is returned.

.PP

.I Strdup

returns a pointer to a distinct copy of the null-terminated string

.I s

in space obtained from

.IR malloc (2)

or

.L 0

if no space can be obtained.

.PP

.I Strstr

returns a pointer to the first occurrence of

.I s2

as a substring of

.IR s1 ,

or 0 if there is none.

If

.I s2

is the null string,

.I strstr

returns

.IR s1 .

.I Cistrstr

operates analogously, but ignores ASCII case differences when comparing strings.

.SH SOURCE

All these routines have portable C implementations in

.BR /sys/src/libc/port .

Many also have machine-dependent assembly language

implementations in

.BR /sys/src/libc/$objtype .

.SH SEE ALSO

.IR memory (2),

.IR rune (2),

.IR runestrcat (2),

.IR string (2)

.SH BUGS

These routines know nothing about

.SM UTF.

Use the routines in

.IR rune (2)

as appropriate.

Note, however, that the definition of

.SM UTF

guarantees that

.I strcmp

compares

.SM UTF

strings correctly.

.PP

The outcome of overlapping moves varies among implementations.