hi all,
Is there any advantage in using FILE* related api calls instead of
using the file descriptor and related calls like read()?
pls share your ideas.

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>Is there any advantage in using FILE* related api calls instead of
>using the file descriptor and related calls like read()?
>pls share your ideas.

The use of, say, getc() and putc() calls or other
single-character-at-a-time I/O operations using stdio can be
significantly faster than single-character read() or write() calls.

If you're doing I/O in large blocks anyway, reading and writing in
64k read() or write() calls might be faster than stdio calls (which
might use a buffer like 512 bytes or 4k or 16k).

This can interact with the sector interleave of floppies and hard
disks to the point that writing a whole floppy as a buffered device
can take 1 minute with stdio and over an hour with
single-character-at-a-time write() calls.

Gordon L. Burditt

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"vineeth" <nvineeth@gmail.com> writes:
> Is there any advantage in using FILE* related api calls instead of
> using the file descriptor and related calls like read()?
> pls share your ideas.

The FILE* calls are defined by the C language standard.  The calls
using file descriptors are not; they're defined by the POSIX standard.
Code using Unix-style file descriptors is less portable than code that
uses only the standard FILE* interface.

(This may not be relevant if you don't care about portability to
non-Unix system.)

--
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
San Diego Supercomputer Center             <*>  <http://users.sdsc.edu/~kst>
We must do something.  This is something.  Therefore, we must do this.

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Keith Thompson wrote:
> "vineeth" <nvineeth@gmail.com> writes: 
>
> The FILE* calls are defined by the C language standard.  The calls
> using file descriptors are not; they're defined by the POSIX standard.
> Code using Unix-style file descriptors is less portable than code that
> uses only the standard FILE* interface.
>
> (This may not be relevant if you don't care about portability to
> non-Unix system.)

Just a note, the file decriptor is a member of the FILE structure. i.e:


typedef struct  {
unsigned char  *curp;	/* Current active pointer (mandatory) */
unsigned char  *buffer;	/* Data transfer buffer	  (mandatory) */
int             level;	/* fill/empty level of buffer	        */
int             bsize;	/* Buffer size            (mandatory) */
unsigned short  istemp;	/* Temporary file indicator   	  */
unsigned short  flags;	/* File status flags      (mandatory) */
wchar_t         hold;	/* ungetc char if no buffer exists    */
char            fd;		/* FILE DESCRIPTOR        (mandatory) */
unsigned char   token;	/* Used for validity checking 	  */
}   FILE;			      /* This is the FILE type

Even the MSDN has its versions of read(2) and write(2) -- using file
descriptors. See:
_write() : http://tinyurl.com/ddon8
_read()  : http://tinyurl.com/9ju9e

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50295@web.de wrote:
> Keith Thompson wrote:
> 
>
>
> Just a note, the file decriptor is a member of the FILE structure. i.e:

on the platform you got that from.

I can promise you that the FILE structure is not the same on all platforms

> Even the MSDN has its versions of read(2) and write(2) -- using file
> descriptors.

/But/, systems like Z/OS (OS/390, MVS, etc.) /do not/ have file descriptors.

- --
Lew Pitcher
IT Specialist, Enterprise Data Systems,
Enterprise Technology Solutions, TD Bank Financial Group

(Opinions expressed are my own, not my employers')
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