归纳整理Linux下C语言常用的库函数----内存及字符串控制及操作

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

• 已经不赞成使用的函数归类

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*           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
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*2. void bcopy(const void *src, void *dest, size_t n);          copy byte sequence                            memcpy Or memmove
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*3. void bzero(void *s, size_t n);                              write zero-valued bytes                       memset
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*4. char *index(const char *s, int c);                          locate character in string                    strchr
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*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.
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*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
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*8. int strcasecmp(const char *s1, const char *s2);             compare two strings ignoring case     UP
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*9. int strncasecmp(const char *s1, const char *s2, size_t n);  compare two strings ignoring case     UP
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* 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
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*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。