字符串相关函数

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;}

 

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;}

 

 

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;}

 

 

 

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;}

 

 

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;}

 

 

 

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;}

 

 

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;}

 

 

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;}

 

 

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);}

 

 

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;}

 

 

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;}

 

 

 

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;}

 

 

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;}

 

 

 

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;}

 

 

 

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[50] = "abcdefghijklmnopqrstuvwxyz";   char letter = 'x';   printf("string before strnset: %s\n", string);   strnset(string, letter, 13);   printf("string after strnset: %s\n", string);   return 0;}

 

 

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;}

 

 

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;}

 

 

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;}

 

 

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;}

 

 

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;}

 

 

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;     p = strtok(input, ",");   if (p)   printf("%s\n", p);     p = strtok(NULL, ",");   if (p)   printf("%s\n", p);   return 0;}

 

 

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;     lnumber = strtol(string, &endptr, 10);   printf("string = %s long = %ld\n", string, lnumber);   return 0;}

 

 

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;     ptr = strupr(string);   printf("%s\n", ptr);   return 0;}

 

 

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;}