包含文件：
string.h
函數名: strstr
函數原型：
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1
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extern
char
*
strstr
(
char
*str1,
const
char
*str2);
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語法：
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1
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*
strstr
(str1,str2)
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str1: 被查找目標 string expression to search.
str2: 要查找對象 The string expression to find.
返回值：若str2是str1的子串，則返回str2在str1的首次出現的地址；如果str2不是str1的子串，則返回NULL。
例子：
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char
str[]=
"1234xyz"
;
char
*str1=
strstr
(str,
"34"
);
cout << str1 << endl;
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顯示的是: 34xyz
函數實現
1.Copyright 1990 Software Development Systems, Inc.
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char
*
strstr
(
const
char
*s1,
const
char
*s2)
{
int
len2;
if
(!(len2=
strlen
(s2)))
//此種情況下s2不能指向空，否則strlen無法測出長度，這條語句錯誤
return
(
char
*)s1;
for
(;*s1;++s1)
{
if
(*s1==*s2 &&
strncmp
(s1,s2,len2)==0)
return
(
char
*)s1;
}
return
NULL;
}
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2.Copyright 1986 - 1999 IAR Systems. All rights reserved
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char
*
strstr
(constchar*s1,constchar*s2)
{
int
n;
if
(*s2)
{
while
(*s1)
{
for
(n=0;*(s1+n)==*(s2+n);n++)
{
if
(!*(s2+n+1))
return
(
char
*)s1;
}
s1++;
}
return
NULL;
}
else
return
(
char
*)s1;
}
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3. GCC-4.8.0
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char
*
strstr
(
const
char
*s1,
const
char
*s2)
{
const
char
*p=s1;
const
size_tlen=
strlen
(s2);
for
(;(p=
strchr
(p,*s2))!=0;p++)
{
if
(
strncmp
(p,s2,len)==0)
return
(
char
*)p;
}
return
(0);
}
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應用舉例
// strstr.c
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#include <syslib.h>
#include <string.h>
main()
{
char
*s=
"GoldenGlobalView"
;
char
*l=
"lob"
;
char
*p;
clrscr();
p=
strstr
(s,l);
if
(p)
printf
(
"%s"
,p);
else
printf
(
"NotFound!"
);
getchar
();
return0;
}
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//功能：從字串” string1 onexxx string2 oneyyy”中尋找”yyy”
(假設xxx和yyy都是一個未知的字串)
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char
*s=”string1onexxxstring2oneyyy”;
char
*p;
p=
strstr
(s,”yyy”);
if
(p!=NULL)
printf
(“%s”,p);
else
printf
(
"notfound\n"
);
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說明：如果直接寫語句p=strstr(s,”one”)，找到的是onexxxstring2oneyyy
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char
*mystrstr(
char
*s1,
char
*s2)
{
if
(*s1==0)
{
if
(*s2)
return
(
char
*)NULL;
return
(
char
*)s1;
}
while
(*s1)
{
int
i=0;
while
(1)
{
if
(s2[i]==0)
return
s1;
if
(s2[i]!=s1[i])
break
;
i++;
}
s1++;
}
return
(
char
*)NULL;
}
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