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