C++strcmp用法

函数名: strcmp 
功 能: 串比较 
用 法: int strcmp(char *str1, char *str2); 
看Asic码，str1>str2，返回值 > 0；两串相等，返回0 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "aaa", *buf2 = "bbb", *buf3 = "ccc"; 
int ptr; 
ptr = strcmp(buf2, buf1); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
else 
printf("buffer 2 is less than buffer 1n"); 
ptr = strcmp(buf2, buf3); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 3n"); 
else 
printf("buffer 2 is less than buffer 3n"); 
return 0; 
}

/*下面再给你其他相关的函数应用*/


函数名: stpcpy 
功 能: 拷贝一个字符串到另一个 
用 法: char *stpcpy(char *destin, char *source); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[10]; 
char *str1 = "abcdefghi"; 
stpcpy(string, str1); 
printf("%sn", string); 
return 0; 
} 

函数名: strcat 
功 能: 字符串拼接函数 
用 法: char *strcat(char *destin, char *source); 
程序例: 
#include  
#include  
int main(void) 
{ 
char destination[25]; 
char *blank = " ", *c = "C++", *Borland = "Borland"; 
strcpy(destination, Borland); 
strcat(destination, blank); 
strcat(destination, c); 
printf("%sn", destination); 
return 0; 
} 

函数名: strchr 
功 能: 在一个串中查找给定字符的第一个匹配之处 
用 法: char *strchr(char *str, char c); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[15]; 
char *ptr, c = 'r'; 
strcpy(string, "This is a string"); 
ptr = strchr(string, c); 
if (ptr) 
printf("The character %c is at position: %dn", c, ptr-string); 
else 
printf("The character was not foundn"); 
return 0; 
}

函数名: strncmpi 
功 能: 将一个串中的一部分与另一个串比较, 不管大小写 
用 法: int strncmpi(char *str1, char *str2, unsigned maxlen); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "BBB", *buf2 = "bbb"; 
int ptr; 
ptr = strcmpi(buf2, buf1); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
if (ptr < 0) 
printf("buffer 2 is less than buffer 1n"); 
if (ptr == 0) 
printf("buffer 2 equals buffer 1n"); 
return 0; 
}

函数名: strcpy 
功 能: 串拷贝 
用 法: char *strcpy(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[10]; 
char *str1 = "abcdefghi"; 
strcpy(string, str1); 
printf("%sn", string); 
return 0; 
}

函数名: strcspn 
功 能: 在串中查找第一个给定字符集内容的段 
用 法: int strcspn(char *str1, char *str2); 
程序例: 
#include  
#include  
#include  
int main(void) 
{ 
char *string1 = "1234567890"; 
char *string2 = "747DC8"; 
int length; 
length = strcspn(string1, string2); 
printf("Character where strings intersect is at position %dn", length); 
return 0; 
}

函数名: strdup 
功 能: 将串拷贝到新建的位置处 
用 法: char *strdup(char *str); 
程序例: 
#include  
#include  
#include  
int main(void) 
{ 
char *dup_str, *string = "abcde"; 
dup_str = strdup(string); 
printf("%sn", dup_str); 
free(dup_str); 
return 0; 
}


函数名: stricmp 
功 能: 以大小写不敏感方式比较两个串 
用 法: int stricmp(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "BBB", *buf2 = "bbb"; 
int ptr; 
ptr = stricmp(buf2, buf1); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
if (ptr < 0) 
printf("buffer 2 is less than buffer 1n"); 
if (ptr == 0) 
printf("buffer 2 equals buffer 1n"); 
return 0; 
}

函数名: strerror 
功 能: 返回指向错误信息字符串的指针 
用 法: char *strerror(int errnum); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buffer; 
buffer = strerror(errno); 
printf("Error: %sn", buffer); 
return 0; 
}

函数名: strcmpi 
功 能: 将一个串与另一个比较, 不管大小写 
用 法: int strcmpi(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "BBB", *buf2 = "bbb"; 
int ptr; 
ptr = strcmpi(buf2, buf1); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
if (ptr < 0) 
printf("buffer 2 is less than buffer 1n"); 
if (ptr == 0) 
printf("buffer 2 equals buffer 1n"); 
return 0; 
}

函数名: strncmp 
功 能: 串比较 
用 法: int strncmp(char *str1, char *str2, int maxlen); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "aaabbb", *buf2 = "bbbccc", *buf3 = "ccc"; 
int ptr; 
ptr = strncmp(buf2,buf1,3); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
else 
printf("buffer 2 is less than buffer 1n"); 
ptr = strncmp(buf2,buf3,3); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 3n"); 
else 
printf("buffer 2 is less than buffer 3n"); 
return(0); 
}

函数名: strncmpi 
功 能: 把串中的一部分与另一串中的一部分比较, 不管大小写 
用 法: int strncmpi(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "BBBccc", *buf2 = "bbbccc"; 
int ptr; 
ptr = strncmpi(buf2,buf1,3); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
if (ptr < 0) 
printf("buffer 2 is less than buffer 1n"); 
if (ptr == 0) 
printf("buffer 2 equals buffer 1n"); 
return 0; 
}

函数名: strncpy 
功 能: 串拷贝 
用 法: char *strncpy(char *destin, char *source, int maxlen); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[10]; 
char *str1 = "abcdefghi"; 
strncpy(string, str1, 3); 
string[3] = ''; 
printf("%sn", string); 
return 0; 
}

函数名: strnicmp 
功 能: 不注重大小写地比较两个串 
用 法: int strnicmp(char *str1, char *str2, unsigned maxlen); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *buf1 = "BBBccc", *buf2 = "bbbccc"; 
int ptr; 
ptr = strnicmp(buf2, buf1, 3); 
if (ptr > 0) 
printf("buffer 2 is greater than buffer 1n"); 
if (ptr < 0) 
printf("buffer 2 is less than buffer 1n"); 
if (ptr == 0) 
printf("buffer 2 equals buffer 1n"); 
return 0; 
}

函数名: strnset 
功 能: 将一个串中的所有字符都设为指定字符 
用 法: char *strnset(char *str, char ch, unsigned n); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *string = "abcdefghijklmnopqrstuvwxyz"; 
char letter = 'x'; 
printf("string before strnset: %sn", string); 
strnset(string, letter, 13); 
printf("string after strnset: %sn", string); 
return 0; 
}

函数名: strpbrk 
功 能: 在串中查找给定字符集中的字符 
用 法: char *strpbrk(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *string1 = "abcdefghijklmnopqrstuvwxyz"; 
char *string2 = "onm"; 
char *ptr; 
ptr = strpbrk(string1, string2); 
if (ptr) 
printf("strpbrk found first character: %cn", *ptr); 
else 
printf("strpbrk didn't find character in setn"); 
return 0; 
}

函数名: strrchr 
功 能: 在串中查找指定字符的最后一个出现 
用 法: char *strrchr(char *str, char c); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[15]; 
char *ptr, c = 'r'; 
strcpy(string, "This is a string"); 
ptr = strrchr(string, c); 
if (ptr) 
printf("The character %c is at position: %dn", c, ptr-string); 
else 
printf("The character was not foundn"); 
return 0; 
}

函数名: strrev 
功 能: 串倒转 
用 法: char *strrev(char *str); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *forward = "string"; 
printf("Before strrev(): %sn", forward); 
strrev(forward); 
printf("After strrev(): %sn", forward); 
return 0; 
}

函数名: strset 
功 能: 将一个串中的所有字符都设为指定字符 
用 法: char *strset(char *str, char c); 
程序例: 
#include  
#include  
int main(void) 
{ 
char string[10] = "123456789"; 
char symbol = 'c'; 
printf("Before strset(): %sn", string); 
strset(string, symbol); 
printf("After strset(): %sn", string); 
return 0; 
}

函数名: strspn 
功 能: 在串中查找指定字符集的子集的第一次出现 
用 法: int strspn(char *str1, char *str2); 
程序例: 
#include  
#include  
#include  
int main(void) 
{ 
char *string1 = "1234567890"; 
char *string2 = "123DC8"; 
int length; 
length = strspn(string1, string2); 
printf("Character where strings differ is at position %dn", length); 
return 0; 
}

函数名: strstr 
功 能: 在串中查找指定字符串的第一次出现 
用 法: char *strstr(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *str1 = "Borland International", *str2 = "nation", *ptr; 
ptr = strstr(str1, str2); 
printf("The substring is: %sn", ptr); 
return 0; 
}

函数名: strtod 
功 能: 将字符串转换为double型值 
用 法: double strtod(char *str, char **endptr); 
程序例: 
#include  
#include  
int main(void) 
{ 
char input[80], *endptr; 
double value; 
printf("Enter a floating point number:"); 
gets(input); 
value = strtod(input, &endptr); 
printf("The string is %s the number is %lfn", input, value); 
return 0; 
}

函数名: strtok 
功 能: 查找由在第二个串中指定的分界符分隔开的单词 
用 法: char *strtok(char *str1, char *str2); 
程序例: 
#include  
#include  
int main(void) 
{ 
char input[16] = "abc,d"; 
char *p; 
/* strtok places a NULL terminator 
in front of the token, if found */ 
p = strtok(input, ","); 
if (p) printf("%sn", p); 
/* A second call to strtok using a NULL 
as the first parameter returns a pointer 
to the character following the token */ 
p = strtok(NULL, ","); 
if (p) printf("%sn", p); 
return 0; 
}

函数名: strtol 
功 能: 将串转换为长整数 
用 法: long strtol(char *str, char **endptr, int base); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *string = "87654321", *endptr; 
long lnumber; 
/* strtol converts string to long integer */ 
lnumber = strtol(string, &endptr, 10); 
printf("string = %s long = %ldn", string, lnumber); 
return 0; 
}

函数名: strupr 
功 能: 将串中的小写字母转换为大写字母 
用 法: char *strupr(char *str); 
程序例: 
#include  
#include  
int main(void) 
{ 
char *string = "abcdefghijklmnopqrstuvwxyz", *ptr; 
/* converts string to upper case characters */ 
ptr = strupr(string); 
printf("%sn", ptr); 
return 0; 
}

函数名: swab 
功 能: 交换字节 
用 法: void swab (char *from, char *to, int nbytes); 
程序例: 
#include  
#include  
#include  
char source[15] = "rFna koBlrna d"; 
char target[15]; 
int main(void) 
{ 
swab(source, target, strlen(source)); 
printf("This is target: %sn", target); 
return 0; 
}

PS:isalpha()是字符函数，不是字符串函数， 
isalpha 
原型：extern int isalpha(int c); 
用法：#include  
功能：判断字符c是否为英文字母 
说明：当c为英文字母a-z或A-Z时，返回非零值，否则返回零。 
举例： 
// isalpha.c 
#include  
#include  
#include  

main() 
{ 
int c; 
clrscr(); // clear screen 
printf("Press a key"); 
for(;;) 
{ 
c=getchar(); 
clrscr(); 
printf("%c: %s letter",c,isalpha(c)?"is":"not"); 
} 
return 0; // just to avoid warnings by compiler 
}
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