STRCAT(2) STRCAT(2)
NAME
strcat, strncat, strcmp, strncmp, cistrcmp, cistrncmp,
strcpy, strncpy, strecpy, strlen, strchr, strrchr, strpbrk,
strspn, strcspn, strtok, strdup, strstr, cistrstr - string
operations
SYNOPSIS
#include <u.h>
#include <libc.h>
char* strcat(char *s1, char *s2)
char* strncat(char *s1, char *s2, long n)
int strcmp(char *s1, char *s2)
int strncmp(char *s1, char *s2, long n)
int cistrcmp(char *s1, char *s2)
int cistrncmp(char *s1, char *s2, int n)
char* strcpy(char *s1, char *s2)
char* strecpy(char *s1, char *es1, char *s2)
char* strncpy(char *s1, char *s2, long n)
long strlen(char *s)
char* strchr(char *s, int c)
char* strrchr(char *s, int c)
char* strpbrk(char *s1, char *s2)
long strspn(char *s1, char *s2)
long strcspn(char *s1, char *s2)
char* strtok(char *s1, char *s2)
char* strdup(char *s)
char* strstr(char *s1, char *s2)
char* cistrstr(char *s1, char *s2)
DESCRIPTION
The arguments s1, s2 and s point to null-terminated strings.
Page 1 Plan 9 (printed 11/24/24)
STRCAT(2) STRCAT(2)
The functions strcat, strncat, strcpy, strecpy, and strncpy
all alter s1. Strcat and strcpy do not check for overflow of
the array pointed to by s1.
Strcat appends a copy of string s2 to the end of string s1.
Strncat appends at most n bytes. Each returns a pointer to
the null-terminated result.
Strcmp compares its arguments and returns an integer less
than, equal to, or greater than 0, according as s1 is lexi-
cographically less than, equal to, or greater than s2.
Strncmp makes the same comparison but examines at most n
bytes. Cistrcmp and cistrncmp ignore ASCII case distinc-
tions when comparing strings. The comparisons are made with
unsigned bytes.
Strcpy copies string s2 to s1, stopping after the null byte
has been copied. Strncpy copies exactly n bytes, truncating
s2 or adding null bytes to s1 if necessary. The result will
not be null-terminated if the length of s2 is n or more.
Each function returns s1.
Strecpy copies bytes until a null byte has been copied, but
writes no bytes beyond es1. If any bytes are copied, s1 is
terminated by a null byte, and a pointer to that byte is
returned. Otherwise, the original s1 is returned.
Strlen returns the number of bytes in s, not including the
terminating null byte.
Strchr (strrchr) returns a pointer to the first (last)
occurrence of byte c in string s, or `0' if c does not occur
in the string. The null byte terminating a string is con-
sidered to be part of the string.
Strpbrk returns a pointer to the first occurrence in string
s1 of any byte from string s2, `0' if no byte from s2 exists
in s1.
Strspn (strcspn) returns the length of the initial segment
of string s1 which consists entirely of bytes from (not
from) string s2.
Strtok considers the string s1 to consist of a sequence of
zero or more text tokens separated by spans of one or more
bytes from the separator string s2. The first call, with
pointer s1 specified, returns a pointer to the first byte of
the first token, and will have written a null byte into s1
immediately following the returned token. The function
keeps track of its position in the string between separate
calls; subsequent calls, signified by s1 being `0', will
work through the string s1 immediately following that token.
Page 2 Plan 9 (printed 11/24/24)
STRCAT(2) STRCAT(2)
The separator string s2 may be different from call to call.
When no token remains in s1, `0' is returned.
Strdup returns a pointer to a distinct copy of the null-
terminated string s in space obtained from malloc(2) or `0'
if no space can be obtained.
Strstr returns a pointer to the first occurrence of s2 as a
substring of s1, or 0 if there is none. If s2 is the null
string, strstr returns s1. Cistrstr operates analogously,
but ignores ASCII case differences when comparing strings.
SOURCE
All these routines have portable C implementations in
/sys/src/libc/port. Many also have machine-dependent assem-
bly language implementations in /sys/src/libc/$objtype.
SEE ALSO
memory(2), rune(2), runestrcat(2), string(2)
BUGS
These routines know nothing about UTF. Use the routines in
rune(2) as appropriate. Note, however, that the definition
of UTF guarantees that strcmp compares UTF strings cor-
rectly.
The outcome of overlapping moves varies among implementa-
tions.
Page 3 Plan 9 (printed 11/24/24)