Detailed Description
Functions | |
| int | close (int fildes) |
| int | open (const char *name, int flags,...) |
| int | read (int fildes, void *buf, size_t nbyte) |
| int | write (int fildes, const void *buf, size_t nbyte) |
| int | ioctl (int fildes, int request,...) |
Function Documentation
| int close | ( | int | fildes | ) |
This function closes the file associated with the specified descriptor.
- Parameters
-
fildes The File descriptor fildes.
- Returns
- Zero on success or -1 on error with errno (see Error Numbers) set to:
- EBADF: Invalid file descriptor
| int ioctl | ( | int | fildes, |
| int | request, | ||
| ... | |||
| ) |
This function performs a control request on the device associated with fildes. request is specific to the device. The value of request determines what value should be passed as the ctl argument.
- Parameters
-
fildes The file descriptor returned by open() request The request to the device.
- Returns
- The number of bytes actually read of -1 with errno (see Error Numbers) set to:
- EBADF: fildes is bad
- EIO: IO error
- EAGAIN: O_NONBLOCK is set for fildes and the device is busy
| int open | ( | const char * | name, |
| int | flags, | ||
| ... | |||
| ) |
This function opens a file with flags being the OR'd combination of:
- O_RDONLY, O_WRONLY or O_RDWR
- O_NONBLOCK, O_CREAT, O_EXCL, O_TRUNC
If the O_CREAT flag is set, the third argument should specify the mode as a mode_t. The bits used with the mode are:
- S_IRWXU: User read/write/execute
- S_IRUSR: User read
- S_IWUSR: User write
- S_IXUSR: User execute
- S_IRWXG: Group read/write/execute
- S_IRGRP: Group read (groups not implemented)
- S_IWGRP: Group write (groups not implemented)
- S_IXGRP: Group execute (groups not implemented)
- S_IRWXO: Other read/write/execute
- S_IROTH: Other read
- S_IWOTH: Other write
- S_IXOTH: Other execute
- Returns
- Zero on success or -1 on error with errno (see Error Numbers) set to:
- ENAMETOOLONG: name exceeds PATH_MAX or a component of name exceeds NAME_MAX
- ENOENT: name could not be found
- EIO: IO error
- EEXIST: name already exists and flags is not set to overwrite
- ENOMEM: not enough memory to open another file
- ENOTDIR: the path to name does not exist
- EFBIG: size error with the file (file is likely corrupt)
| int read | ( | int | fildes, |
| void * | buf, | ||
| size_t | nbyte | ||
| ) |
This function reads nbyte bytes from fildes to the memory location pointed to by buf.
read() is always a synchronous call which is either blocking or non-blocking depending on the value of O_NONBLOCK for fildes.
- Parameters
-
fildes The file descriptor returned by open() buf A pointer to the destination memory (process must have write access) nbyte The number of bytes to read
- Returns
- The number of bytes actually read of -1 with errno (see Error Numbers) set to:
- EBADF: fildes is bad
- EACCESS: fildes is on in O_WRONLY mode
- EIO: IO error
- EAGAIN: O_NONBLOCK is set for fildes and no new data is available
| int write | ( | int | fildes, |
| const void * | buf, | ||
| size_t | nbyte | ||
| ) |
This function writes nbyte bytes fildes from the memory location pointed to by buf.
write() is always a synchronous call which is either blocking or non-blocking depending on the value of O_NONBLOCK for fildes.
- Parameters
-
fildes The file descriptor returned by open() buf A pointer to the destination memory (process must have write access) nbyte The number of bytes to read
- Returns
- The number of bytes actually read of -1 with errno (see Error Numbers) set to:
- EBADF: fildes is bad
- EACCESS: fildes is on in O_RDONLY mode
- EIO: IO error
- EAGAIN: O_NONBLOCK is set for fildes and the device is busy