操作字符串的 C 函数

心已赠人 2022-08-19 14:15 167阅读 0赞

函数名: strcpy

功 能: 拷贝一个字符串到另一个字符串  
用 法: char \*strcpy(char \*destin, char \*source);  
程序例:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <string.h> ＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <string.h>  
＃i nclude <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: strcasecmp  
功 能: 以大小写不敏感方式比较两个串  
用 法: int strcasecmp (char \*str1, char \*str2);  
程序例:  
＃i nclude <string.h>  
＃i nclude <stdio.h>  
int main(void)  
\{  
char \*buf1 = "BBB", \*buf2 = "bbb";  
int ptr;  
ptr = strcasecmp (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:  
＃i nclude <stdio.h>  
＃i nclude <errno.h>  
int main(void)  
\{  
char \*buffer;  
buffer = strerror(errno);  
printf("Error: %s/n", buffer);  
return 0;  
\}  
函数名: strcasecmp   
功 能: 将一个串与另一个比较, 不管大小写  
用 法: int strcasecmp (char \*str1, char \*str2);  
程序例:  
＃i nclude <string.h>  
＃i nclude <stdio.h>  
int main(void)  
\{  
char \*buf1 = "BBB", \*buf2 = "bbb";  
int ptr;  
ptr = strcasecmp (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:  
＃i nclude <string.h>  
＃i nclude <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: strncasecmp   
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 strncasecmp (char \*str1, char \*str2);  
程序例:  
＃i nclude <string.h>  
＃i nclude <stdio.h>  
int main(void)  
\{  
char \*buf1 = "BBBccc", \*buf2 = "bbbccc";  
int ptr;  
ptr = strncasecmp (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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <stdlib.h>  
int main(void)  
\{  
char input\[80\], \*endptr;  
double ;  
printf("Enter a floating point number:");  
gets(input);  
= strtod(input, &endptr);  
printf("The string is %s the number is %lf/n", input, );  
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:  
＃i nclude <string.h>  
＃i nclude <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:  
＃i nclude <stdlib.h>  
＃i nclude <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:  
＃i nclude <stdio.h>  
＃i nclude <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:  
＃i nclude <stdlib.h>  
＃i nclude <stdio.h>  
＃i nclude <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;

注：文中的几个大小写不敏感比较函数，原文用的是stricmp等，后来发现linux的std库没有，改为strcasecmp系列。