System Calls

Functions
int	_open (const char *path, int oflag,...)
	Open file. More...
int	_close (int fildes)
	Close a file descriptor. More...
ssize_t	_write (int fildes, const void *buf, size_t nbyte)
	Write on a file. More...
ssize_t	_read (int fildes, void *buf, size_t nbyte)
	Read from a file. More...
off_t	_lseek (int fildes, off_t offset, int whence)
	Move the read/write file offset. More...
int	_isatty (int fildes)
	Test for a terminal device. More...
int	_fstat (int fildes, struct stat *buf)
	Get file status. More...
int	_stat (const char *path, struct stat *buf)
	Get file status (by name). More...
int	_link (const char *path1, const char *path2)
	Link one file to another file. More...
int	_unlink (const char *path)
	Remove a directory entry. More...
int	_execve (const char *path, char *const argv[], char *const envp[])
	Execute a file. More...
pid_t	fork (void)
	Create a new process. More...
void	_exit (int status)
	Terminate a process. More...
int	_kill (pid_t pid, int sig)
	Send a signal to a process or a group of processes. More...
pid_t	_getpid (void)
	Get the process ID. More...
pid_t	_wait (int *stat_loc)
	Wait for a child process to stop or terminate. More...
void *	_sbrk (ptrdiff_t incr)
	Extend heap space by incr bytes. More...

Variables
char **	environ
	A pointer to an array of character pointers to the environment strings. More...

Description

Function Documentation

_close()

int _close

(

int

fildes

)

Close a file descriptor.

Parameters

[in]

fildes

File descriptor

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_execve()

int _execve	(	const char *	path,
		char *const	argv[],
		char *const	envp[]
	)

Execute a file.

Parameters

[in]	path	Pathname that identifies the new process image file
[in]	argv	Pointers to strings that constitute process argument list
[in]	envp	Pointers to strings that constitute process environment variables

Returns

If the function returns an error occured, -1 is returned and errno is set to indicate the error.

_exit()

void _exit

(

int

status

)

Terminate a process.

Parameters

[in]

status

Process exit status code

_fstat()

int _fstat	(	int	fildes,
		struct stat *	buf
	)

Get file status.

Parameters

[in]	fildes	File descriptor
[out]	buf	A pointer to a stat structure

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_getpid()

pid_t _getpid

(

void

)

Get the process ID.

Returns

Process ID (function is always successful).

_isatty()

int _isatty

(

int

fildes

)

Test for a terminal device.

Parameters

[in]

fildes

File descriptor

Returns

The return value is 1 if fildes is associated with a terminal. Otherwise, 0 is returned.

_kill()

int _kill	(	pid_t	pid,
		int	sig
	)

Send a signal to a process or a group of processes.

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_link()

int _link	(	const char *	path1,
		const char *	path2
	)

Link one file to another file.

Parameters

[in]	path1	Pathname naming an existing file
[out]	path2	Pathname naming the new directory entry to be created

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_lseek()

off_t _lseek	(	int	fildes,
		off_t	offset,
		int	whence
	)

Move the read/write file offset.

Parameters

[in]	fildes	File descriptor
[in]	offset	File offset
[in]	whence	File seek mode

Returns

Upon successful completion, the resulting offset in bytes from the beginning of the file is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_open()

int _open	(	const char *	path,
		int	oflag,
			...
	)

Open file.

Parameters

[in]	path	Pathname naming the file
[in]	oflag	Mode specification bitmap

Returns

Upon successful completion, function opens the file and returns a non-negative integer representing the file descriptor. Otherwise, the function returns -1 and sets errno to indicate the error.

_read()

ssize_t _read	(	int	fildes,
		void *	buf,
		size_t	nbyte
	)

Read from a file.

Parameters

[in]	fildes	File descriptor
[out]	buf	A pointer to data buffer
[in]	nbyte	Number of bytes to read

Returns

Upon successful completion, function returns a non-negative integer indicating the number of bytes actually read. Otherwise, the function returns -1 and sets errno to indicate the error.

_sbrk()

void * _sbrk

(

ptrdiff_t

incr

)

Extend heap space by incr bytes.

Parameters

[in]

incr

The number of bytes to increment the heap by

Returns

Upon successful completion, a pointer to the start of the new block of memory is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_stat()

int _stat	(	const char *	path,
		struct stat *	buf
	)

Get file status (by name).

Parameters

[in]	path	Pathname naming the file
[in]	buf	A pointer to a stat structure

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_unlink()

int _unlink

(

const char *

path

)

Remove a directory entry.

Parameters

[in]

path

Pathname naming the file

Returns

Upon successful completion, 0 is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_wait()

pid_t _wait

(

int *

stat_loc

)

Wait for a child process to stop or terminate.

Parameters

[in]

stat_loc

Pointer to a integer to store status information

Returns

If function returns because the status of a child process is available, the child process ID is returned. Otherwise, the function returns -1 and sets errno to indicate the error.

_write()

ssize_t _write	(	int	fildes,
		const void *	buf,
		size_t	nbyte
	)

Write on a file.

Parameters

[in]	fildes	File descriptor
[in]	buf	A pointer to data buffer
[in]	nbyte	Number of bytes to write

Returns

Upon successful completion, this function returns the number of bytes actually written to the file associated with fildes. Otherwise, the function returns -1 and sets errno to indicate the error.

fork()

pid_t fork

(

void

)

Create a new process.

Returns

Upon successful completion:

• 0 is returned to the child process.
• process ID of the child process is returned to the parent process. Otherwise, -1 is returned and sets errno to indicate the error.

Variable Documentation

environ

char ** environ

extern

A pointer to an array of character pointers to the environment strings.