Files in C

Files

Devices represented as files

If file can be physical device, not fixed in size or behavior

Streams are associated with files

May support file position indicator [0,length]

Binary or not

Can be closed, opened, flushed

Can be buffered, unbuffered, line buffered

Unbuffered - i/o immediate

Fully buffered - i/o accumulated into block, then passed

Line buffered - block size depends on \n

Each file opened has a file descriptor (fd)

fd describes state of file

Opened, closed, position etc

FILE --- a struct defined in stdio.h

Functions

-fopen (const char* path, const char* mode);

-fscanf(stdin,....) == scanf

-fprintf(stdout,....) == printf

-fread

-fwrite

-fclose

-fgets

-feof(stream), does not happen until beyond stream

When program begins, special files

-stdin, stdout, stderr are opened

If file position supported, position == 0

Print, scan adjusts position in stream

Get position == ftell, change position == fseek

Setvbuf defines how a stream should be buffered

int setvbuf (FILE* stream, char* buffer, int mode, size_t size)

Modes

- _IOFBF -- full

- _IOLBF -- line

- _IONBF -- no buffering

Size

Buffer size in bytes