Low-Level I/O
These functions invoke the operating system directly for lower-level operation than that provided by stream I/O. Low-level input and output calls do not buffer or format data.
Low-level routines can access the standard streams opened at program startup using the following predefined file descriptors.
Stream |
File Descriptor |
|---|---|
stdin |
0 |
stdout |
1 |
stderr |
2 |
Low-level I/O routines set the errno global variable when an error occurs. You must include STDIO.H when you use low-level functions only if your program requires a constant that is defined in STDIO.H, such as the end-of-file indicator (EOF).
Low-Level I/O Functions
Function |
Use |
|---|---|
Close file |
|
Flush file to disk |
|
Create file |
|
Return next available file descriptor for given file |
|
Create second descriptor for given file |
|
Test for end of file |
|
Reposition file pointer to given location |
|
Open file |
|
Read data from file |
|
Open file for file sharing |
|
Get current file-pointer position |
|
Set file-permission mask |
|
Write data to file |
_dup and _dup2 are typically used to associate the predefined file descriptors with different files.