str函数族

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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char string[10]; 
    char *str1 = "abcdefghi";   stpcpy(string, str1); 
    printf("%s\n", 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 <string.h> 
 #include <stdio.h>int main(void) 
 { 
    char destination[25]; 
    char *blank = " ", *c = "C++", *Borland = "Borland";   strcpy(destination, Borland); 
    strcat(destination, blank); 
    strcat(destination, c);   printf("%s\n", 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 <string.h> 
 #include <stdio.h>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: %d\n", c, ptr-string); 
     else 
        printf("The character was not found\n"); 
     return 0; 
 }

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 <string.h> 
 #include <stdio.h>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 1\n"); 
     else 
        printf("buffer 2 is less than buffer 1\n");    ptr = strcmp(buf2, buf3); 
     if (ptr > 0) 
        printf("buffer 2 is greater than buffer 3\n"); 
     else 
        printf("buffer 2 is less than buffer 3\n");    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 <string.h> 
 #include <stdio.h>int main(void) 
 { 
    char *buf1 = "BBB", *buf2 = "bbb"; 
    int ptr;   ptr = strcmpi(buf2, buf1);
   if (ptr > 0) 
       printf("buffer 2 is greater than buffer 1\n");   if (ptr < 0) 
       printf("buffer 2 is less than buffer 1\n");   if (ptr == 0) 
       printf("buffer 2 equals buffer 1\n");   return 0; 
 }

函数名: strcpy
功 能: 串拷贝
用 法: char *strcpy(char *str1, char *str2);
程序例:

#include <stdio.h> 
 #include <string.h>int main(void) 
 { 
     char string[10]; 
     char *str1 = "abcdefghi";    strcpy(string, str1); 
     printf("%s\n", 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 <stdio.h> 
 #include <string.h> 
 #include <alloc.h>int main(void) 
 { 
     char *string1 = "1234567890"; 
     char *string2 = "747DC8"; 
     int length;    length = strcspn(string1, string2); 
     printf("Character where strings intersect is at position %d\n", 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 <stdio.h> 
 #include <string.h> 
 #include <alloc.h>int main(void) 
 { 
     char *dup_str, *string = "abcde";    dup_str = strdup(string); 
     printf("%s\n", 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 <string.h> 
 #include <stdio.h>int main(void) 
 { 
    char *buf1 = "BBB", *buf2 = "bbb"; 
    int ptr;   ptr = stricmp(buf2, buf1);
   if (ptr > 0) 
       printf("buffer 2 is greater than buffer 1\n");   if (ptr < 0) 
       printf("buffer 2 is less than buffer 1\n");   if (ptr == 0) 
       printf("buffer 2 equals buffer 1\n");   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 <stdio.h> 
 #include <errno.h>int main(void) 
 { 
    char *buffer; 
    buffer = strerror(errno); 
    printf("Error: %s\n", 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 <string.h> 
 #include <stdio.h>int main(void) 
 { 
    char *buf1 = "BBB", *buf2 = "bbb"; 
    int ptr;   ptr = strcmpi(buf2, buf1);
   if (ptr > 0) 
       printf("buffer 2 is greater than buffer 1\n");   if (ptr < 0) 
       printf("buffer 2 is less than buffer 1\n");   if (ptr == 0) 
       printf("buffer 2 equals buffer 1\n");   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 <string.h> 
 #include <stdio.h>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 1\n"); 
    else 
       printf("buffer 2 is less than buffer 1\n");   ptr = strncmp(buf2,buf3,3); 
    if (ptr > 0) 
       printf("buffer 2 is greater than buffer 3\n"); 
    else 
       printf("buffer 2 is less than buffer 3\n");   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 <string.h> 
 #include <stdio.h>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 1\n");   if (ptr < 0) 
       printf("buffer 2 is less than buffer 1\n");   if (ptr == 0) 
       printf("buffer 2 equals buffer 1\n");   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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char string[10]; 
    char *str1 = "abcdefghi";   strncpy(string, str1, 3); 
    string[3] = '\0'; 
    printf("%s\n", 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 <string.h> 
 #include <stdio.h>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 1\n");   if (ptr < 0) 
       printf("buffer 2 is less than buffer 1\n");   if (ptr == 0) 
       printf("buffer 2 equals buffer 1\n");   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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char *string = "abcdefghijklmnopqrstuvwxyz"; 
    char letter = 'x';   printf("string before strnset: %s\n", string); 
    strnset(string, letter, 13); 
    printf("string after strnset: %s\n", 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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char *string1 = "abcdefghijklmnopqrstuvwxyz"; 
    char *string2 = "onm"; 
    char *ptr;   ptr = strpbrk(string1, string2);
   if (ptr) 
       printf("strpbrk found first character: %c\n", *ptr); 
    else 
       printf("strpbrk didn't find character in set\n");   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 <string.h> 
 #include <stdio.h>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: %d\n", c, ptr-string); 
    else 
       printf("The character was not found\n"); 
    return 0; 
 }

函数名: strrev
功 能: 串倒转
用 法: char *strrev(char *str);
程序例:

#include <string.h> 
 #include <stdio.h>int main(void) 
 { 
    char *forward = "string";   printf("Before strrev(): %s\n", forward); 
    strrev(forward); 
    printf("After strrev(): %s\n", 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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char string[10] = "123456789"; 
    char symbol = 'c';   printf("Before strset(): %s\n", string); 
    strset(string, symbol); 
    printf("After strset(): %s\n", 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 <stdio.h> 
 #include <string.h> 
 #include <alloc.h>int main(void) 
 { 
    char *string1 = "1234567890"; 
    char *string2 = "123DC8"; 
    int length;   length = strspn(string1, string2); 
    printf("Character where strings differ is at position %d\n", 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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char *str1 = "Borland International", *str2 = "nation", *ptr;   ptr = strstr(str1, str2); 
    printf("The substring is: %s\n", 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 <stdio.h> 
 #include <stdlib.h>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 %lf\n", 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 <string.h> 
 #include <stdio.h>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("%s\n", 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("%s\n", 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 <stdlib.h> 
 #include <stdio.h>int main(void) 
 { 
    char *string = "87654321", *endptr; 
    long lnumber;   /* strtol converts string to long integer */ 
    lnumber = strtol(string, &endptr, 10); 
    printf("string = %s long = %ld\n", 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 <stdio.h> 
 #include <string.h>int main(void) 
 { 
    char *string = "abcdefghijklmnopqrstuvwxyz", *ptr;   /* converts string to upper case characters */ 
    ptr = strupr(string); 
    printf("%s\n", 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 <stdlib.h> 
 #include <stdio.h> 
 #include <string.h>char source[15] = "rFna koBlrna d"; 
 char target[15];int main(void) 
 { 
    swab(source, target, strlen(source)); 
    printf("This is target: %s\n", target); 
    return 0;

原型：extern char *strstr(char *haystack, char *needle);
所在头文件：#include <string.h>
功能：从字符串haystack中寻找needle第一次出现的位置（不比较结束符NULL)。
说明：返回指向第一次出现needle位置的指针，如果没找到则返回NULL。

具体使用例子：

1. #include <stdio.h>
2. #include <string.h> 
3. 
4. int main(int argc,char **argv)
5. {
6. char *haystack="aaa||a||bbb||c||ee||";
7. char *needle="||";
8. char* buf = strstr( haystack,  needle);
9. while( buf != NULL )
10. {
11. buf[0]='\0';
12. printf( "%s\n ", haystack);
13. haystack = buf + strlen(needle);
14. /* Get next token: */
15. buf = strstr( haystack,  needle);
16. }
17.    return 0;
18. }