unistd.h File Reference

#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>
#include "kconfig.h"

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Macros
#define	MQ_PRIO_MAX   _MQ_PRIO_MAX
#define	STDIN_FILENO   0 /* Standard input file descriptor */
#define	STDOUT_FILENO   1 /* Standard output file descriptor */
#define	STDERR_FILENO   2 /* Standard error file descriptor */

Functions
unsigned int	sleep (unsigned int seconds)
	To cause the calling thread to sleep either until the number of real-time seconds specified in seconds have elapsed or until a signal arrives which is not ignored. More...
int	usleep (useconds_t usec)
	Suspend execution of the calling thread for a given time in microseconds. More...
int	close (int fd)
	Close a file descriptor, so that it no longer refers to any file and may be reused. More...
int	dup (int oldfd)
	Create a copy of the file descriptor oldfd, using the lowest-numbered unused file descriptor for the new descriptor. More...
int	dup2 (int oldfd, int newfd)
	Perform the same task as dup(), but use the file descriptor number specified by newfd. More...
ssize_t	read (int fd, void *buf, size_t count)
	Attempt to read up to count bytes from file descriptor fd into the buffer starting at buf. More...
ssize_t	write (int fd, const void *buf, size_t count)
	Write up to count bytes from the buffer starting at buf to the file referred to by the file descriptor fd. More...
off_t	lseek (int fd, long offset, int whence)
	Reposition the file offset of the open file description associated with the file descriptor fd. More...
int	getpid (void)
	Return the ID of the calling task. More...
char *	getcwd (char *buf, size_t size)
	Get current working directory. More...
int	chdir (const char *path)
	Change working directory. More...

Function Documentation

chdir()

int chdir

(

const char *

path

)

Change working directory.

Parameters

path	Pathname of the new working directory.

Return values

int	0 on success and nonzero error number on error.

close()

int close

(

int

fd

)

Close a file descriptor, so that it no longer refers to any file and may be reused.

Parameters

fd	The file descriptor to provide.

Return values

int	0 on success and nonzero error number on error.

dup()

int dup

(

int

oldfd

)

Create a copy of the file descriptor oldfd, using the lowest-numbered unused file descriptor for the new descriptor.

Parameters

oldfd

The file descriptor to duplicate.

Return values

int	New file descriptor on success and nonzero error number on error.

dup2()

int dup2	(	int	oldfd,
		int	newfd
	)

Perform the same task as dup(), but use the file descriptor number specified by newfd.

Parameters

oldfd	The file descriptor to duplicate.
newfd	The number to specify the new file descriptor.

Return values

int	New file descriptor on success and nonzero error number on error.

getcwd()

char* getcwd	(	char *	buf,
		size_t	size
	)

Get current working directory.

Parameters

buf	Buffer space for storing path of the current working space.
size	Size of the buffer space.

Return values

char	*: The function returns a pointer to a string containing the pathname of current working directory if success; otherwise it returns NULL.

getpid()

int getpid

(

void

)

Return the ID of the calling task.

Parameters

None

Return values

int

Task ID.

lseek()

off_t lseek	(	int	fd,
		long	offset,
		int	whence
	)

Reposition the file offset of the open file description associated with the file descriptor fd.

Parameters

fd	The file descriptor to provide.
offset	The new offset to the position specified by whence.
whence	The start position of the new offset.

Return values

int	0 on success and nonzero error number on error.

read()

ssize_t read	(	int	fd,
		void *	buf,
		size_t	count
	)

Attempt to read up to count bytes from file descriptor fd into the buffer starting at buf.

Parameters

fd	The file descriptor to provide.
buf	The memory space for storing read data.
count	The number of bytes to read.

Return values

int	0 on success and nonzero error number on error.

sleep()

unsigned int sleep

(

unsigned int

seconds

)

To cause the calling thread to sleep either until the number of real-time seconds specified in seconds have elapsed or until a signal arrives which is not ignored.

Parameters

seconds

The sleep seconds to provide.

Return values

int	0 on success and nonzero error number on error.

usleep()

int usleep

(

useconds_t

usec

)

Suspend execution of the calling thread for a given time in microseconds.

Parameters

usec	The sleep microseconds to provide.

Return values

int	0 on success and nonzero error number on error.

write()

ssize_t write	(	int	fd,
		const void *	buf,
		size_t	count
	)

Write up to count bytes from the buffer starting at buf to the file referred to by the file descriptor fd.

Parameters

fd	The file descriptor to provide.
buf	The data to write.
count	The number of bytes to write.

Return values

int	0 on success and nonzero error number on error.