c字符串函数

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;
}