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.TH STRING 3
.CT 2 data_man
.SH NAME
strcat, strncat, strcmp, strncmp, strcpy, strncpy, strlen,
strchr, strrchr, strpbrk, strspn, strcspn, strtok, strdup \(mi string operations
.SH SYNOPSIS
.nf
.2C
.B #include <libc.h>
.PP
.B char *strcat(s1, s2)
.B char *s1, *s2;
.PP
.B char *strncat(s1, s2, n)
.B char *s1, *s2;
.B int n;
.PP
.B int strcmp(s1, s2)
.B char *s1, *s2;
.PP
.B int strncmp(s1, s2, n)
.B char *s1, *s2;
.B int n;
.PP
.B char *strcpy(s1, s2)
.B char *s1, *s2;
.PP
.B char *strncpy(s1, s2, n)
.B char *s1, *s2;
.B int n;
.PP
.B int strlen(s)
.B char *s;
.PP
.B char *strchr(s, c)
.B char *s;
.B int c;
.PP
.B char *strrchr(s, c)
.B char *s;
.B int c;
.PP
.B char *strpbrk(s1, s2)
.B char *s1, *s2;
.PP
.B int strspn(s1, s2)
.B char *s1, *s2;
.PP
.B int strcspn(s1, s2)
.B char *s1, *s2;
.PP
.B char *strtok(s1, s2)
.B char *s1, *s2;
.PP
.B char *strdup(s)
.B char *s;
.sp
.1C
.SH DESCRIPTION
The arguments
.I s1, s2
and
.I s
point to null-terminated strings.
The functions
.IR strcat ,
.IR strncat ,
.IR strcpy ,
and
.I strncpy
all alter
.IR s1 .
These functions 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
characters.
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 looks at at most
.I n
characters.
.PP
.I Strcpy
copies string
.I s2
to
.IR s1 ,
stopping after the null character has been copied.
.I Strncpy
copies exactly
.I n
characters,
truncating
.I s2
or adding
null characters 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 Strlen
returns the number of characters in
.IR s ,
not including the terminating null character.
.PP
.I Strchr
.RI ( strrchr )
returns a pointer to the first (last)
occurrence of character
.I c
in string
.IR s ,
or
.L (char *)0
if
.I c
does not occur in the string.
The null character 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 character from string
.IR s2 ,
.L (char *)0
if no character 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 characters 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 characters from the separator string
.IR s2 .
The first call, with pointer
.I s1
specified, returns a pointer to the first character of the first
token, having replaced the character after the token by 0.
Subsequent calls,
signified by
.I s1
being
.LR "(char *)0" ,
will scan from where the preceding call left off.
The separator string
.I s2
may be different from call to call.
When no token remains in
.IR s1 ,
.L (char *)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 (3)
or
.L (char *)0
if no space can be obtained.
.SH SEE ALSO
.IR memory (3)
.SH BUGS
.I Strcmp
and
.I strncmp
use native character comparison, which may
be signed or unsigned.
.br
The outcome of overlapping moves varies among implementations.
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