fcntl - manipulate file descriptorfcntl - 操作文件描述符所需头文件#include #include int fcntl(int fd, int cmd, ... /* arg */ );fcntl() performs one of the operations described below on the ope

brk, sbrk - change data segment sizebrk，sbrk-改变数据段的大小所需头文件：#include int brk(void *addr);void *sbrk(intptr_t increment);brk()  and  sbrk()  change the location of the program break, w

malloc, free, calloc, realloc - allocate and free dynamic memorymalloc，free，calloc，realloc-动态分配和释放内存所需头文件#include void *malloc(size_t size);void free(void *ptr);void *calloc(size_t nme

getpass - get a passwordgetpass - 获取一个密码所需头文件：#include char *getpass( const char *prompt);This function is obsolete.  Do not use it.这个函数已经被废弃，请勿使用The  getpass()  function  opens 

所需头文件#include alloca：allocate memory that is automatically freed申请能够自动释放的内存（实际上是栈区的内存）void *alloca(size_t size);The  alloca()  function  allocates size bytes of space in the stack frame

所需头文件#include int atoi(const char *nptr);long atol(const char *nptr);long long atoll(const char *nptr);long long atoq(const char *nptr);The atoi() function converts the initial portion

setfsuid - set user identity used for file system checkssetfsuid - 为文件系统设置用户id所需头文件#include /* glibc uses */int setfsuid(uid_t fsuid);The system call setfsuid() sets the user ID that

isalnumchecks for an alphanumeric character; it is equivalent to (isalpha(c) || isdigit(c)).检查是否是含有字母或者数字的字符，等同于isalpha||isdigitisalphachecks  for  an alphabetic character; in the standard "

setgid - set group identitysetgid - 设置组id所需头文件#include #include int setgid(gid_t gid);setgid() sets the effective group ID of the calling process.  If the caller is the superuser, th

seteuid, setegid - set effective user or group IDseteuid, setegid - 设置有效的用户和组id所需头文件#include #include int seteuid(uid_t euid);int setegid(gid_t egid);seteuid()  sets  the effective

getpagesize - get memory page sizegetpagesize-获取内存页大小所需头文件：#include int getpagesize(void);The  function getpagesize() returns the number of bytes in a memory page, where "page" is a fi

asctime, ctime, gmtime, localtime, mktime, asctime_r, ctime_r, gmtime_r, localtime_r - transform date and time to broken-down time or ASCIIasctime,ctimegmtime,localtime,mktime,asctime_r,ctime_r,gm

clearerr, feof, ferror, fileno - check and reset stream statusclearerr, feof, ferror, fileno - 检查和重置流状态所需头文件#include void clearerr(FILE *stream);int feof(FILE *stream);int ferror(FILE *s

mkstemp, mkostemp, mkstemps, mkostemps - create a unique temporary filemkstemp, mkostemp, mkstemps, mkostemps - 创建一个唯一的临时文件所需头文件#include int mkstemp(char *template);int mkostemp(char *temp

flock - apply or remove an advisory lock on an open fileflock - 添加或者移除咨询性文件锁所需头文件#include int flock(int fd, int operation);Apply or remove an advisory lock on the open file specified b

sync, syncfs - commit buffer cache to disksync, syncfs - 提交buffer缓冲到磁盘所需头文件#include void sync(void);void syncfs(int fd);Feature Test Macro Requirements for glibc (see feature_test_

lseek - reposition read/write file offsetlseek - 重定位读/写文件偏移量所需头文件#include #include off_t lseek(int fd, off_t offset, int whence);The  lseek()  function repositions the offset of the

dup, dup2, dup3 - duplicate a file descriptordup, dup2, dup3 - 复制一个文件描述符所需头文件#include int dup(int oldfd);int dup2(int oldfd, int newfd);#define _GNU_SOURCE             /* See feature

write - write to a file descriptorwrite - 写到一个文件描述符所需头文件#include ssize_t write(int fd, const void *buf, size_t count);write() writes up to count bytes from the buffer pointed buf to

open, creat - open and possibly create a file or deviceopen, creat - 打开和可能创建一个文件或者设备所需头文件#include #include #include int open(const char *pathname, int flags);int open(const char *pat

read - read from a file descriptorread - 从一个文件描述符中读所需头文件#include ssize_t read(int fd, void *buf, size_t count);read() attempts to read up to count bytes from file descriptor fd into

close - close a file descriptorclose - 关闭一个文件描述符所需头文件#include int close(int fd);close()  closes  a file descriptor, so that it no longer refers to any file and may be reused.  Any re

fgetpwent - get password file entryfgetpwent - 获取密码文件的入口所需头文件#include #include #include struct passwd *fgetpwent(FILE *stream);The  fgetpwent()  function returns a pointer to a str

getpwnam, getpwnam_r, getpwuid, getpwuid_r - get password file entrygetpwnam, getpwnam_r, getpwuid, getpwuid_r - 获取password文件的入口所需头文件#include #include struct passwd *getpwnam(const char

strdup, strndup, strdupa, strndupa - duplicate a stringstrdup, strndup, strdupa, strndupa -复制一个字符串所需头文件#include char *strdup(const char *s);char *strndup(const char *s, size_t n);char

strlen - calculate the length of a string计算字符串的长度所需头文件#include size_t strlen(const char *s);The strlen() function calculates the length of the string s, excluding the terminating null

strcpy, strncpy - copy a string复制一个字符串所需头文件#include char *strcpy(char *dest, const char *src);char *strncpy(char *dest, const char *src, size_t n);The  strcpy()  function copies the

strspn, strcspn - search a string for a set of bytesstrspn,strcspn-在字符串中查找字节序列所需头文件#include size_t strspn(const char *s, const char *accept);size_t strcspn(const char *s, const char *rej

strcat, strncat - concatenate two stringsstrcat,strncat-连接两个字符串所需头文件#include char *strcat(char *dest, const char *src);char *strncat(char *dest, const char *src, size_t n);The  strcat(

strcmp, strncmp - compare two stringsstrcmp,strncmp-比较两个字符串所需头文件#include int strcmp(const char *s1, const char *s2);int strncmp(const char *s1, const char *s2, size_t n);The  strcmp() 

memcpy - copy memory areamemcpy-复制内存所需头文件#include void *memcpy(void *dest, const void *src, size_t n);The  memcpy() function copies n bytes from memory area src to memory area dest.  T

bcmp - compare byte sequencesbcmp-比较字节序列所需头文件#include int bcmp(const void *s1, const void *s2, size_t n);The  bcmp()  function compares the two byte sequences s1 and s2 of length n eac

index, rindex - locate character in stringindex,rindex-在字符串中定位字符所需头文件#include char *index(const char *s, int c);char *rindex(const char *s, int c);The index() function returns a pointe

strtok, strtok_r - extract tokens from stringsstrtok,strtok_r-从字符串中提取标记所需头文件：#include char *strtok(char *str, const char *delim);char *strtok_r(char *str, const char *delim, char **savep

strpbrk - search a string for any of a set of bytes所需头文件#include char *strpbrk(const char *s, const char *accept);The strpbrk() function locates the first occurrence in the string s of a

strstr, strcasestr - locate a substring定位子串所需头文件#include char *strstr(const char *haystack, const char *needle);#define _GNU_SOURCE         /* See feature_test_macros(7) */#include

getpw - reconstruct password line entrygetpw - 重建password行入口所需头文件#define _GNU_SOURCE             /* See feature_test_macros(7) */#include #include int getpw(uid_t uid, char *buf);T

getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entrygetgrnam, getgrnam_r, getgrgid, getgrgid_r - 获取group文件的入口所需头文件#include #include struct group *getgrnam(const char *name);

getgroups, setgroups - get/set list of supplementary group IDsgetgroups, setgroups - 获取/设置附加组id的列表所需头文件#include #include int getgroups(int size, gid_t list[]);#include int setgroups(

updwtmp, logwtmp - append an entry to the wtmp fileupdwtmp, logwtmp - 增加入口到wtmp文件尾部所需头文件#include void updwtmp(const char *wtmp_file, const struct utmp *ut);void logwtmp(const char *line,