常用函数说明

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: 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: memset

功 能: 设置s中的所有字节为ch, s数组的大小由n给定

用 法: void *memset(void *s, char ch, unsigned n);

程序例:

#include <string.h>

#include <stdio.h>

#include <mem.h>

int main(void)

{

char buffer[] = "Hello world/n";

printf("Buffer before memset: %s/n", buffer);

memset(buffer, '*', strlen(buffer) - 1);

printf("Buffer after memset: %s/n", buffer);

return 0;

}

函数名: atof

功 能: 把字符串转换成浮点数

用 法: double atof(const char *nptr);

程序例:

#include <stdlib.h>

#include <stdio.h>

int main(void)

{

float f;

char *str = "12345.67";

f = atof(str);

printf("string = %s float = %f/n", str, f);

return 0;

}

函数名: fcvt

功 能: 把一个浮点数转换为字符串

用 法: char *fcvt(double value, int ndigit, int *decpt, int *sign);

程序例:

#include <stdlib.h>

#include <stdio.h>

#include <conio.h>

int main(void)

{

char *string;

double value;

int dec, sign;

int ndig = 10;

clrscr();

value = 9.876;

string = ecvt(value, ndig, &dec, &sign);

printf("string = %s dec = %d /

sign = %d/n", string, dec, sign);

value = -123.45;

ndig= 15;

string = ecvt(value,ndig,&dec,&sign);

printf("string = %s dec = %d sign = %d/n",

string, dec, sign);

value = 0.6789e5; /* scientific

notation */

ndig = 5;

string = ecvt(value,ndig,&dec,&sign);

printf("string = %s dec = %d/

sign = %d/n", string, dec, sign);

return 0;

}

函数名:
gcvt

功 能: 把浮点数转换成字符串

用 法: char *gcvt(double value, int ndigit, char *buf);

程序例:

#include <stdlib.h>

#include <stdio.h>

int main(void)

{

char str[25];

double num;

int sig = 5; /* significant digits */

/* a regular number */

num = 9.876;

gcvt(num, sig, str);

printf("string = %s/n", str);

/* a negative number */

num = -123.4567;

gcvt(num, sig, str);

printf("string = %s/n", str);

/* scientific notation */

num = 0.678e5;

gcvt(num, sig, str);

printf("string = %s/n", str);

return(0);

}

函数名: itoa

功 能: 把一整数转换为字符串

用 法: char *itoa(int value, char *string, int radix);

程序例:

#include <stdlib.h>

#include <stdio.h>

int main(void)

{

int number = 12345;

char string[25];

itoa(number, string, 10);

printf("integer = %d string = %s/n", number, string);

return 0;

}