c语言编写6个字符串处理函数
时间: 2024-05-07 12:21:42 浏览: 9
1. strlen:计算字符串长度
```
int strlen(char *str) {
int len = 0;
while (*str++) {
len++;
}
return len;
}
```
2. strcpy:拷贝字符串
```
void strcpy(char *dest, char *src) {
while ((*dest++ = *src++)) {
;
}
}
```
3. strcat:连接字符串
```
void strcat(char *dest, char *src) {
while (*dest) {
dest++;
}
while ((*dest++ = *src++)) {
;
}
}
```
4. strcmp:比较字符串
```
int strcmp(char *s1, char *s2) {
while (*s1 && (*s1 == *s2)) {
s1++;
s2++;
}
return *(unsigned char *)s1 - *(unsigned char *)s2;
}
```
5. strstr:查找字符串
```
char *strstr(char *str, char *substr) {
int substr_len = strlen(substr);
while (*str) {
if (strncmp(str, substr, substr_len) == 0) {
return str;
}
str++;
}
return NULL;
}
```
6. strtok:分割字符串
```
char *strtok(char *str, char *delim) {
static char *p = NULL;
if (str != NULL) {
p = str;
} else if (p == NULL) {
return NULL;
}
char *start = p;
while (*p && !strchr(delim, *p)) {
p++;
}
if (*p) {
*p++ = '\0';
}
return start;
}
```