Begining Linux Programing Chapter 3

/dev/console  

Error messages and diagnostics are often sent to this device.

/dev/tty

It is an alias for the controlling terminal of a process.

/dev/null

All output written to this device is discarded.

Library Functions:

The library functions arrange for the low-level system calls .

Permission:

The mode value given in the open call is ANDed with the inverse of the user mask value at runtime.

ioctl:

It provides an interface for controlling the behavior of devices and their descriptors and configuring underlying services.

The standard I/O library:

The equivalent of the low-level file descriptor is called a stream is implemnted as a pointer to a structure, a FILE *.

Three file streams are automatically opened when a program is strarted.They are stdin,stdout,stderr.

fclose:

To close the specified stream,causing any unwritten data to be fgwritten.When a program ends normally,fclose is called automatically on all file streams that are still open.

fflush:

causing all outstanding data on a file stream to be  written immediately. f

fgets:

read a string from an input file stream.

Streams Error:

The ferror function tests the error indicator for a stream and returns nonzero if it's set,but zero otherwise.

The feof function tests the end-of-file indicator within a stream and returns nonzero if it is set,zero otherwise.

The clearerr function clears the end-of-file and error indicators for the stream to which stream points.

Error:

strerror,maps an error number into a string describing the type of error that has occurred.

perror,report in errno,into a string and prints it on the standard error stream.