在没有IDE的时候，记住一些常用的库函数的函数名、参数、基本用法及注意事项是很有必要的。
参照Linux_C_HS.chm的目录，我大致将常用的函数分为一下几类：
- 1. 内存及字符串控制及操作
- 2. 字符串转换
- 3. 字符测试
- 4. 文件操作
- 5. 时间日期
- 6. 常用数学函数
- 7. 文件内容操作
- 8. 文件权限控制
- 9. 进程操作
- 10. 线程操作
- 11. Socket操作
- 12. 信号处理
- 13. 数据结构及算法
以下是对第一项 内存及字符串控制及操作 的归纳整理。
- 已经不赞成使用的函数归类
* * 函数名 用途 替换方案 *1. int bcmp(const void *s1, const void *s2, size_t n); compare byte sequences memcmp * *2. void bcopy(const void *src, void *dest, size_t n); copy byte sequence memcpy Or memmove * *3. void bzero(void *s, size_t n); write zero-valued bytes memset * *4. char *index(const char *s, int c); locate character in string strchr * *5. char *rindex(const char *s, int c); locate character in string strrchr *
- 内存或字符串查找函数归类
* 函数名 用途 备注 *1. void *memchr(const void *s, int c, size_t n); scan memory for a character (Forward) return a pointer to the matching byte or NULL if the character does not occur in the given memory area. * *2. void *memrchr(const void *s, int c, size_t n); scan memory for a character (Backward) return a pointer to the matching byte or NULL if the character does not occur in the given memory area. * *3. char *strchr(const char *s, int c); locate character in string (Forward) return a pointer to the matched character or NULL if the character is not found. * *4. char *strrchr(const char *s, int c); locate character in string (Backward) return a pointer to the matched character or NULL if the character is not found. * *5. char *strstr(const char *haystack, const char *needle); locate a substring return a pointer to the beginning of the substring, or NULL if the substring is not found. * *6. char *strcasestr(const char *haystack, const char *needle); locate a substring,ignores the return a pointer to the beginning of the substring, case of both arguments. or NULL if the substring is not found. *
- 内存及字符串拷贝、比较函数归类
* 函数名 用途 备注 * *1. void *memcpy(void *dest, const void *src, size_t n); copy memory area The memcpy() function returns a pointer to dest. * *2. char *strcpy(char *dest, const char *src); copy a string return a pointer to the destination string dest. * *3. char *strncpy(char *dest, const char *src, size_t n); copy a string return a pointer to the destination string dest. * *4. void *memmove(void *dest, const void *src, size_t n); copy memory area , may overlap returns a pointer to dest. * *5. int memcmp(const void *s1, const void *s2, size_t n); compare memory areas returns an integer less than, equal to, or greater than zero if the first n bytes of s1 is found * *6. int strcmp(const char *s1, const char *s2); compare two strings return an integer less than, equal to, or greater than zero if s1 is foundfound * *7. int strncmp(const char *s1, const char *s2, size_t n); compare two strings UP * *8. int strcasecmp(const char *s1, const char *s2); compare two strings ignoring case UP * *9. int strncasecmp(const char *s1, const char *s2, size_t n); compare two strings ignoring case UP * * 10. char *strdup(const char *s); duplicate a string returns a pointer to a new string which is a duplicate of the string s. Memory for the new string is obtained with *
- 内存或字符串连接、分割、求长等函数归类
* 函数名 用途 备注 *1. char *strcat(char *dest, const char *src); concatenate two strings return a pointer to the resulting string dest * *2. char *strncat(char *dest, const char *src, size_t n); UP UP * *3. char *strtok(char *str, const char *delim); extract tokens from strings 第一次调用时，str必须不为空，第二次调用str必须为空 * *4. char *strtok_r(char *str, const char *delim, char **saveptr); 可重入函数，线程安全 推荐使用这个分割函数，具体讨论见http://blog.csdn.net/liuintermilan/article/details/6283705 *
以上，就是对第一项的整理归纳。接下来，会对第二项 字符串转换 进行归纳。