C语言字符串操作常用库函数

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);

举例： char fullname="./lib/lib1.so"; char *ptr; ptr = strrchr(fullname,'/'); printf("filename is %s",++ptr); //运行结果：filename is lib1.so

 

函数名: strchr
功  能: 在串中查找指定字符的第一个出现
用  法: char *strchr(char *str, char c);

举例：char fullname="./lib/lib1.so"; char *ptr; ptr = strrchr(fullname,'.'); printf("after strchr() is %s",++ptr); //运行结果：after strchr() is /lib/lib1.so

 

函数名: strtok
功  能: 在串中查找指定字符的第一个出现
用  法: char *strtok(char *s, char *delim);

说明：

1.strtok函数的实质上的处理是，strtok在s中查找包含在delim中的字符并用NULL(’/0′)来替换,直到找遍整个字符串。这句话有两层含义：（1）每次调用strtok函数只能获得一个分割单位。（2）要获得所有的分割单元必须反复调用strtok函数。

2.strtok函数以后的调用时的需用NULL来替换s.

3.形参s(要分割的字符串)对应的变量应用char s[]=”….”形式，而不能用char *s=”….”形式。

举例：void main() { char buf[]=”Golden Global View”; char* token = strtok( buf, ” “); while( token != NULL ) { printf( ”%s “, token ); token = strtok( NULL, ” “); } return 0; } /*其结果为： Golden Global View */

 

函数名：strncpy

功能：把src所指由NULL结束的字符串的前n个字节复制到dest所指的数组中

用法：char *strncpy(char *dest, char *src, int n);

说明：    

        如果src的前n个字节不含NULL字符，则结果不会以NULL字符结束。
        如果src的长度小于n个字节，则以NULL填充dest直到复制完n个字节。
        src和dest所指内存区域不可以重叠且dest必须有足够的空间来容纳src的字符串。
        返回指向dest的指针。

举例： #include <syslib.h> #include <string.h> main() { char buf[4]; char *s="abcdefg"; strncpy(buf,s,4); printf("%s/n",buf); return 0; } /*运行结果： abcd */

 

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);

举例：#include <stdio.h> #include <string.h> int main(void) { char string[10]; char *str1 = "abcdefghi"; stpcpy(string, str1); printf("%s/n", string); return 0; } /*运行结果 abcdefghi */

 

函数名: strcat
功  能: 字符串拼接函数
用  法: char *strcat(char *destin, char *source);
举例：#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; } /*运行结果： Borland C++ */

 

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

举例：#include <string.h> #include <stdio.h> int main(void) { char *buf1 = "aaa", *buf2 = "bbb"； int ptr; ptr = strcmp(buf2, buf1); if (ptr > 0) printf("buffer 2 is greater than buffer 1/n"); else if(ptr < 0) printf("buffer 2 is less than buffer 1/n"); else printf("buffer 2 is equal with buffer 1/n"); return 0; } /*运行结果： buffer 2 is greater than buffer 1 */

 

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);

举例：#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: 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);
举例：#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);
举例：#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);
举例：#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);
举例：#include <stdio.h> #include <errno.h> int main(void) { char *buffer; buffer = strerror(errno); printf("Error: %s/n", buffer); return 0; }

 

函数名: strncmp
功  能: 串比较
用  法: int strncmp(char *str1, char *str2, int maxlen);
举例：#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, int len);

举例：#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: 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);
举例：#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);
举例：#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: strrev
功  能: 串倒转
用  法: char *strrev(char *str);
举例：#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; } /*运行结果： Before strrev(): string After strrev(): gnirts */

 

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);
举例：#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);
举例：#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: strtol
功  能: 将串转换为长整数
用  法: long strtol(char *str, char **endptr, int base);
举例：#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);
举例：#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; }