POSIX Support

Basic Concepts

The OpenHarmony kernel uses the musl libc library and self-developed APIs and supports the Portable Operating System Interface (POSIX). You can develop components and applications working on the kernel based on the POSIX.

Development Guidelines

Available APIs

Table 1 Available APIs

Category	Header File	API	Description
process	#include <stdlib.h>	void abort(void);	Terminates the thread.
	#include <assert.h>	void assert(scalar expression);	Terminates the thread if the assertion is false.
	#include <pthread.h>	int pthread_cond_destroy(pthread_cond_t *cond);	Destroys a condition variable.
	#include <pthread.h>	int pthread_cond_init(pthread_cond_t restrict cond, const pthread_condattr_t restrict attr);	Initializes a condition variable.
	#include <pthread.h>	int pthread_condattr_getpshared(const pthread_condattr_t attr, int shared);	Obtains condition variable attributes. Currently, only the attributes of PTHREAD_PROCESS_PRIVATE can be obtained.
	#include <pthread.h>	int pthread_condattr_setpshared(pthread_condattr_t *attr, int shared);	Sets a condition variable attribute.
	#include <pthread.h>	int pthread_condattr_getclock(const pthread_condattr_t attr, clockid_t clock);	Obtains the thread clock.
	#include <pthread.h>	int pthread_condattr_destroy(pthread_condattr_t *attr);	Destroys a condition variable and invalidates the attribute object.
	#include <pthread.h>	int pthread_cond_timedwait(pthread_cond_t restrict cond, pthread_mutex_t restrict mutex, const struct timespec *restrict abstime);	Waits for the condition.
	#include <pthread.h>	int pthread_condattr_init(pthread_condattr_t *attr);	Initializes the condition variable attribute.
	#include <pthread.h>	int pthread_mutex_unlock(pthread_mutex_t *mutex);	Unlocks a mutex.
	#include <pthread.h>	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg);	Creates a thread.
	#include <pthread.h>	int pthread_join(pthread_t thread, void **retval);	Waits for a thread to terminate.
	#include <pthread.h>	pthread_t pthread_self(void);	Obtains the ID of the current thread.
	#include <pthread.h>	int pthread_getschedparam(pthread_t thread, int policy, struct sched_param param);	Obtains the scheduling policy and parameters of a thread.
	#include <pthread.h>	int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param *param);	Sets a scheduling policy and parameters for a thread.
	#include <pthread.h>	int pthread_setschedprio(pthread_t thread, int prio);	Sets the thread priority.
	#include <pthread.h>	int pthread_once(pthread_once_t onceControl, void (initRoutine)(void));	Performs one-time initialization routine.
	#include <pthread.h>	int pthread_setcancelstate(int state, int *oldState);	Sets the cancel switch for the thread.
	#include <pthread.h>	int pthread_setcanceltype(int type, int *oldType);	Sets the thread cancel type.
	#include <pthread.h>	int pthread_cancel(pthread_t thread);	Cancels a thread. Currently, a thread can be cancelled only by setting the PTHREAD_CANCEL_ASYNCHRONOUS status and then calling pthread_cancel.
	#include <pthread.h>	void pthread_testcancel(void);	Cancels this thread.
	#include <pthread.h>	int pthread_equal(pthread_t thread1, pthread_t thread2);	Checks whether the two thread IDs are equal.
	#include <pthread.h>	int pthread_mutexattr_gettype(const pthread_mutexattr_t attr, int outType);	Obtains the mutex type attribute.
	#include <pthread.h>	int pthread_mutex_init(pthread_mutex_t __restrict m, const pthread_mutexattr_t __restrict a);	Initializes a mutex.
	#include <pthread.h>	int pthread_mutex_lock(pthread_mutex_t *m);	Locks a mutex.
	#include <pthread.h>	int pthread_mutex_timedlock(pthread_mutex_t mutex, const struct timespec absTimeout);	Requests a mutex (blocked only within the specified period).
	#include <pthread.h>	int pthread_mutex_trylock(pthread_mutex_t *m);	Attempts to lock a mutex.
	#include <pthread.h>	int pthread_mutex_destroy(pthread_mutex_t *m);	Destroys a mutex.
	#include <pthread.h>	int pthread_attr_init(pthread_attr_t *attr);	Initializes a thread attribute object.
	#include <pthread.h>	int pthread_attr_destroy(pthread_attr_t *attr);	Destroys a thread attribute object.
	#include <pthread.h>	int pthread_attr_getstacksize(const pthread_attr_t attr, size_t stacksize);	Obtains the stack size of a thread attribute object.
	#include <pthread.h>	int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize);	Sets the stack size for a thread attribute object.
	#include <pthread.h>	int pthread_attr_setstack(pthread_attr_t attr, void stackAddr, size_t stackSize);	Sets the stack attribute for a thread attribute object (not implemented yet).
	#include <pthread.h>	int pthread_attr_getstack(const pthread_attr_t attr, void stackAddr, size_t stackSize);	Obtains the stack of a thread attribute object (not implemented yet).
	#include <pthread.h>	int pthread_attr_getschedparam(const pthread_attr_t attr, struct sched_param param);	Obtains scheduling parameter attributes of a thread attribute object.
	#include <pthread.h>	int pthread_attr_setschedparam(pthread_attr_t attr, const struct sched_param param);	Sets scheduling parameter attributes for a thread attribute object.
	#include <pthread.h>	int pthread_getname_np(pthread_t pthread, char *name, size_t len);	Obtains the thread name.
	#include <pthread.h>	int pthread_setname_np(pthread_t pthread, const char *name);	Sets the thread name.
	#include <pthread.h>	int pthread_cond_broadcast(pthread_cond_t *c);	Unblocks all threads that are currently blocked on the condition variable cond.
	#include <pthread.h>	int pthread_cond_signal(pthread_cond_t *c);	Unblocks a thread.
	#include <pthread.h>	int pthread_cond_wait(pthread_cond_t __restrict c, pthread_mutex_t __restrict m);	Waits for the condition.
fs	#include <libgen.h>	char dirname(char path);	Obtains the directory name.
	#include <dirent.h>	struct dirent readdir(DIR dirp);	Reads a directory.
	#include <sys/stat.h>	int stat(const char restrict path, struct stat restrict buf);	Obtains file information.
	#include <unistd.h>	int unlink(const char *pathname);	Deletes a file.
	#include <fcntl.h	int open(const char *path, int oflags, ...);	Opens a file. If the file does not exist, create a file and open it.
	#include <nistd.h>	int close(int fd);	Closes a file.
	#include <stdio.h>	int rename(const char oldpath, const char newpath);	Renames a file.
	#include <dirent.h>	DIR opendir(const char dirname);	Opens the specified directory.
	#include <dirent.h>	int closedir(DIR *dir);	Closes the specified directory.
	#include <sys/mount.h>	int mount(const char source, const char target, const char filesystemtype, unsigned long mountflags, const void data);	Mounts a file system.
	#include <sys/mount.h>	int umount(const char *target);	Unmounts a file system.
	#include <sys/mount.h>	int umount2(const char *target, int flag);	Unmounts a file system.
	#include <sys/stat.h>	int fsync(int fd);	Synchronizes the file associated with the specified file descriptor to the storage device.
	#include <sys/stat.h>	int mkdir(const char *pathname, mode_t mode);	Creates a directory.
	#include <unistd.h>	int rmdir(const char *path);	Deletes a directory.
	#include <sys/stat.h>	int fstat(int fd, struct stat *buf);	Obtains file status.
	#include <sys/statfs.h>	int statfs(const char path, struct statfs buf);	Obtains the file system information for a file in a specified path.
time	#include <sys/time.h>	int gettimeofday(struct timeval tv, struct timezone tz);	Obtains the time. Currently, time zone is not supported, and the return value of tz is empty.
	#include <time.h>	struct tm gmtime(const time_t timep);	Converts the date and time to broken-down time or ASCII.
	#include <time.h>	struct tm localtime(const time_t timep);	Obtains the local time.
	#include <time.h>	struct tm localtime_r(const time_t timep, struct tm *result);	Obtains the local time.
	#include <time.h>	time_t mktime(struct tm *tm);	Converts the date and time to broken-down time or ASCII.
	#include <time.h>	size_t strftime(char s, size_t max, const char format,const struct tm *tm);	Formats the date and time.
	#include <time.h>	time_t time(time_t *tloc);	Obtains the calendar time.
	#include <sys/times.h>	clock_t times(struct tms *buf);	Obtains the thread time.
	#include <sys/times.h>	int timer_getoverrun(timer_t timerID);	Obtains the number of timer timeout times.
	#include <unistd.h>	int usleep(useconds_t usec);	Goes to hibernation, in microseconds.
	#include <time.h>	int nanosleep(const struct timespec tspec1, struct timespec tspec2);	Suspends the current thread till the specified time.
	#include <time.h>	int clock_gettime(clockid_t id, struct timespec *tspec);	Obtains the clock time.
	#include <time.h>	int timer_create(clockid_t id, struct sigevent __restrict evp, timer_t __restrict t);	Creates a timer for a thread.
	#include <time.h>	int timer_delete(timer_t t);	Deletes the timer for a thread.
	#include <time.h>	int timer_settime(timer_t t, int flags, const struct itimerspec __restrict val, struct itimerspec __restrict old);	Sets a timer for a thread.
	#include <time.h>	time_t time (time_t *t);	Obtains the time.
	#include <time.h>	char strptime(const char s, const char format, struct tm tm);	Converts the time string into the time tm structure.
util	#include <stdlib.h>	int atoi(const char *nptr);	Converts the string pointed to by nptr into an integer (int type).
	#include <stdlib.h>	long atol(const char *nptr);	Converts the string pointed to by nptr into a long Integer (long type).
	#include <stdlib.h>	long long atoll(const char *nptr);	Converts the string pointed to by nptr into a long long Integer (long long type).
	#include <ctype.h>	int isalnum(int c);	Checks whether the passed character is alphanumeric.
	#include <ctype.h>	int isascii(int c);	Checks whether the passed character is an ASCII character.
	#include <ctype.h>	int isdigit(int c);	Checks whether the passed character is a digit.
	#include <ctype.h>	int islower(int c);	Checks whether the passed character is in lowercase.
	#include <ctype.h>	int isprint(int c);	Checks whether the passed character is printable, including spaces.
	#include <ctype.h>	int isspace(int c);	Checks whether the passed character is a white-space character.
	#include <ctype.h>	int isupper(int c);	Checks whether the passed character is in uppercase.
	#include <ctype.h>	int isxdigit(int c);	Checks whether the passed character is a hexadecimal number.
	#include <stdlib.h>	long int random (void);	Generates a pseudo-random number.
	#include <stdlib.h>	void srandom(unsigned int seed);	Initializes the random number generator.
	#include <ctype.h>	int tolower(int c);	Converts the given letter to lowercase.
	#include <ctype.h>	int toupper(int c);	Converts the given letter to uppercase.
	#include <stdarg.h>	type va_arg(va_list ap, type);	Retrieves the next argument in the parameter list with type.
	#include <stdarg.h>	void va_copy(va_list dest, va_list src);	Copies parameters.
	#include <stdarg.h>	void va_end(va_list ap);	Clears the variable list.
	#include <stdarg.h>	void va_start(va_list ap, last);	Defines the beginning of the list of variable arguments.
	#include <string.h>	char strchr(const char s, int c);	Searches for the first occurrence of a character in a string.
	#include <string.h>	int strcmp(const char s1, const char s2);	Compares two strings.
	#include <string.h>	size_t strcspn(const char s, const char reject);	Obtains the length of the initial segment of the string s which does not contain any of bytes in the string reject.
	#include <string.h>	char strdup(const char s);	Copies a string to a new position.
	#include <string.h>	size_t strlen(const char *s);	Obtains the length of a string.
	#include <strings.h>	int strncasecmp(const char s1, const char s2, size_t n);	Compares the bytes of the specified length in two strings, ignoring case.
	#include <strings.h>	int strcasecmp(const char s1, const char s2);	Compares two strings, ignoring case.
	#include <string.h>	int strncmp(const char s1, const char s2, size_t n);	Compares the bytes of the specified length in two strings.
	#include <string.h>	char strrchr(const char s, int c);	Searches for the last occurrence of a character in a string.
	#include <string.h>	char strstr(const char haystack, const char *needle);	Searches for the specified substring in a string.
	#include <stdlib.h>	long int strtol(const char nptr, char *endptr, int base);	Converts the string pointed to by nptr into a long int value according to the given base.
	#include <stdlib.h>	unsigned long int strtoul(const char nptr, char *endptr, int base);	Converts the string pointed to by nptr into an unsigned long int value according to the given base.
	#include <stdlib.h>	unsigned long long int strtoull(const char nptr, char *endptr,int base);	Converts the string pointed to by nptr into an unsigned long long int value according to the given base.
	#include <regex.h>	int regcomp(regex_t preg, const char regex, int cflags);	Compiles a regular expression.
	#include <regex.h>	int regexec(const regex_t preg, const char string, size_t nmatch,regmatch_t pmatch[], int eflags);	Executes the compiled regular expression.
	#include <regex.h>	void regfree(regex_t *preg);	Releases the regular expression.
	#include <string.h>	char *strerror(int errnum);	Obtains an error message string of the specified error code.
math	#include <stdlib.h>	int abs(int i);	Obtains the absolute value.
	#include <math.h>	double log(double x);	Obtains the natural logarithm (base-e logarithm) of x.
	#include <math.h>	double pow(double x, double y);	Obtains x raised to the power of y.
	#include <math.h>	double round(double x);	Rounds off the value from zero to the nearest integer.
	#include <math.h>	double sqrt(double x);	Obtains the square root of x.
IO	#include <stdio.h>	void clearerr(FILE *stream);	Clears the file end and error indication of a stream.
	#include <stdio.h>	int fclose(FILE *stream);	Closes a file stream.
	#include <stdio.h>	FILE fdopen(int fd, const char mode);	Opens a file stream based on the file descriptor.
	#include <stdio.h>	int feof(FILE *stream);	Checks the end-of-file indicator for a stream.
	#include <stdio.h>	int fflush(FILE *stream);	Flushes a stream.
	#include <stdio.h>	char fgets(char s, int size, FILE *stream);	Reads the next line of a stream.
	#include <stdio.h>	int fileno(FILE *stream);	Obtains the file descriptor for a stream.
	#include <stdio.h>	FILE fopen(const char path, const char *mode);	Opens a stream.
	#include <stdio.h>	int fputs(const char s, FILE stream);	Writes a line to the specified stream.
	#include <stdio.h>	size_t fread(void ptr, size_t size, size_t nmemb, FILE stream);	Reads a stream.
	#include <stdio.h>	int fseek(FILE *stream, long offset, int whence);	Sets the position of the stream pointer.
	#include <stdio.h>	long ftell(FILE *stream);	Obtains the position of the stream pointer.
	#include <stdio.h>	size_t fwrite(const void ptr, size_t size, size_t nmemb,FILE stream);	Writes data to a stream.
	#include <stdio.h>	void perror(const char *s);	Prints system error information.
	#include <stdio.h>	void rewind(FILE *stream);	Sets the position to the beginning of the file of the specified stream.
	#include <unistd.h>	ssize_t write(int fd, const void *buf, size_t size);	Writes data a file.
	#include <unistd.h>	ssize_t read(int fd, void *buf, size_t size);	Reads data from a file.
net	#include <sys/socket.h>	void freeaddrinfo(struct addrinfo *res);	Releases the dynamic memory allocated using getaddrinfo.
	#include <sys/socket.h>	int getaddrinfo(const char restrict nodename,const char restrict servname,const struct addrinfo restrict hints,struct addrinfo *restrict res);	Obtains a list of IP addresses and port numbers for the specified host and service.
	#include <sys/socket.h>	int getnameinfo(const struct sockaddr restrict sa, socklen_t salen,char restrict node, socklen_t nodelen, char *restrict service,socklen_t servicelen, int flags);	Converts a socketaddr structure to a pair of host name and service strings.
	#include <net/if.h>	unsigned int if_nametoindex(const char *ifname);	Obtains the index based on the network port name.
	#include <arpa/inet.h>	in_addr_t inet_addr(const char *cp);	Converts the network host address in dotted decimal notation to binary format.
	#include <arpa/inet.h>	char *inet_ntoa(struct in_addr in);	Converts the network host address in binary format to dotted decimal notation.
	#include <arpa/inet.h>	const char inet_ntop(int af, const void src,char *dst, socklen_t size);	Converts the network address in binary format to text.
	#include <arpa/inet.h>	int inet_pton(int af, const char src, void dst);	Converts the network address in standard text format to numeric binary format.
	#include <sys/socket.h>	int listen(int sockfd, int backlog);	Listens for connections on a socket.
	#include <sys/socket.h>	ssize_t recvmsg(int sockfd, struct msghdr *msg, int flags);	Receives a message from a socket. Currently, only the scenario with iov of 1 is supported and ancillary messages are not supported.
	#include <sys/socket.h>	ssize_t send(int sockfd, const void *buf, size_t len, int flags);	Sends a message on a socket.
	#include <sys/socket.h>	ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags);	Sends a message on a socket. Ancillary messages are not supported.
	#include <sys/socket.h>	ssize_t sendto(int sockfd, const void buf, size_t len, int flags,const struct sockaddr dest_addr, socklen_t addrlen);	Sends a message on a socket.
	#include <sys/socket.h>	int setsockopt(int sockfd, int level, int optname,const void *optval, socklen_t optlen);	Sets options associated with a socket.
mem	#include <string.h>	int memcmp(const void s1, const void s2, size_t n);	Compares successive elements from two arrays until it finds elements that are different.
	#include <string.h>	void memcpy(void dest, const void *src, size_t n);	Copies n bytes from the source memory area pointed to by src to the destination memory area pointed to by dest.
	#include <string.h>	void memset(void s, int c, size_t n);	Initializes memory.
	#include <stdlib.h>	void realloc(void ptr, size_t size);	Reallocates memory.
	#include <stdlib.h>	void *malloc(size_t size);	Dynamically allocates memory blocks.
	#include <stdlib.h>	void free(void *ptr);	Release the memory space pointed to by ptr.
IPC	#include <semaphore.h>	int sem_timedwait(sem_t sem, const struct timespec abs_timeout);	Locks the semaphore referenced by sem as in the sem_wait() function.
	#include <semaphore.h>	int sem_destroy(sem_t *sem);	Destroys the specified unnamed semaphore.
	#include <semaphore.h>	int sem_trywait(sem_t *sem);	Attempts to apply for a semaphore.
	#include <semaphore.h>	int sem_init(sem_t *sem, int pshared, unsigned int value);	Creates and initializes an unnamed semaphore.
	#include <semaphore.h>	int sem_post(sem_t *sem);	Increments the semaphore count by 1.
	#include <semaphore.h>	int sem_wait(sem_t *sem);	Obtains the semaphore.
	#include <mqueue.h>	mqd_t mq_open(const char *mqName, int openFlag, ...);	Opens an existing message queue with the specified name or creates a message queue.
	#include <mqueue.h>	int mq_close(mqd_t personal);	Closes a message queue with the specified descriptor.
	#include <mqueue.h>	int mq_unlink(const char *mqName);	Deletes the message queue of the specified name.
	#include <mqueue.h>	int mq_send(mqd_t personal, const char *msg, size_t msgLen, unsigned int msgPrio);	Puts a message with the specified content and length into a message queue.
	#include <mqueue.h>	ssize_t mq_receive(mqd_t personal, char msg, size_t msgLen, unsigned int msgPrio);	Deletes the oldest message from a message queue and puts it in the buffer pointed to by msg_ptr.
	#include <mqueue.h>	int mq_timedsend(mqd_t personal, const char msg, size_t msgLen, unsigned int msgPrio, const struct timespec absTimeout)	Puts a message with the specified content and length into a message queue at the specified time.
	#include <mqueue.h>	ssize_t mq_timedreceive(mqd_t personal, char msg, size_t msgLen, unsigned int msgPrio, const struct timespec *absTimeout);	Obtains a message with the specified content and length from a message queue.
	#include <mqueue.h>	int mq_setattr(mqd_t mqdes, const struct mq_attr __restrict newattr, struct mq_attr __restrict oldattr);	Sets the message queue attributes specified by the descriptor.
version	#include <libc.h>	const char *libc_get_version_string(void);	Obtains the libc version string.
	#include <libc.h>	int libc_get_version(void);	Obtains the libc version.

Important Notes

Error codes

C Name	Value	Description
ENOERR	0	Success
EPERM	1	Operation not permitted
ENOENT	2	No such file or directory
ESRCH	3	No such process
EINTR	4	Interrupted system call
EIO	5	I/O error
ENXIO	6	No such device or address
E2BIG	7	Arg list too long
ENOEXEC	8	Exec format error
EBADF	9	Bad file number
ECHILD	10	No child processes
EAGAIN	11	Try again
ENOMEM	12	Out of memory
EACCES	13	Permission denied
EFAULT	14	Bad address
ENOTBLK	15	Block device required
EBUSY	16	Device or resource busy
EEXIST	17	File exists
EXDEV	18	Cross-device link
ENODEV	19	No such device
ENOTDIR	20	Not a directory
EISDIR	21	Is a directory
EINVAL	22	Invalid argument
ENFILE*	23	File table overflow
EMFILE	24	Too many open files
EFBIG	27	File too large
ENOSPC	28	No space left on device
ESPIPE	29	Illegal seek
EROFS	30	Read-only file system
EMLINK	31	Too many links
EDOM	33	Math argument out of domain
ERANGE	34	Math result not representable
EDEADLK	35	Resource deadlock would occur
ENAMETOOLONG	36	Filename too long
ENOLCK	37	No record locks available
ENOSYS	38	Function not implemented
ENOTEMPTY	39	Directory not empty
ELOOP	40	Too many symbolic links encountered
ENOMSG	42	No message of desired type
EIDRM	43	Identifier removed
ELNRNG	48	Link number out of range
EBADR	53	Invalid request descriptor
EBADRQC	56	Invalid request code
ENOSTR	60	Device not a stream
ENODATA	61	No data available
ETIME	62	Timer expired
EPROTO	71	Protocol error
EBADMSG	74	Not a data message
EOVERFLOW	75	Value too large for defined data type
EMSGSIZE	90	Message too long

Development Example

Demo:

Creates a thread, transfers the information in the parent thread to the child thread, and prints the transferred information and the thread ID in the child thread.

#include <stdio.h>
#include <pthread.h>

pthread_t ntid;

void *ThreadFn(void *arg)
{
    pthread_t tid;
    while(1) {
        tid = pthread_self();
        printf("\n++++++++++++++  %s  %s  tid = %d ++++++++++++++\n", (char*)arg, __FUNCTION__, tid);
    }
    return ((void *)0);
}

void DemoForTest()
{
    int err;
    char* str = "Hello world";
    err = pthread_create(&ntid, NULL, ThreadFn, (void*)str);
    if(err != 0) {
        printf("can't create thread\n");
    }
}

The execution result of DemoForTest is as follows:

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++

++++++++++++++  Hello world  ThreadFn  tid = 48 ++++++++++++++