How to fputc 'EOF' to a FILE stream.

[oksuresh]

Hi talents,

I have a situation where , I should keep on reading a FILE stream until
a location. And I have to immediately write the EOF character , so that
the rest of the file is cleared.

Any idea?....

Thanks in Advance
Suresh

[Ben Pfaff]

ok******@gmail. com writes:

I have a situation where , I should keep on reading a FILE stream until
a location. And I have to immediately write the EOF character , so that
the rest of the file is cleared.

This is a FAQ.

19.13: How can a file be shortened in-place without completely clearing
or rewriting it?

A: BSD systems provide ftruncate(), several others supply chsize(),
and a few may provide a (possibly undocumented) fcntl option
F_FREESP. Under MS-DOS, you can sometimes use write(fd, "", 0).
However, there is no portable solution, nor a way to delete
blocks at the beginning. See also question 19.14.
--
int main(void){char p[]="ABCDEFGHIJKLM NOPQRSTUVWXYZab cdefghijklmnopq rstuvwxyz.\
\n",*q="kl BIcNBFr.NKEzjwC IxNJC";int i=sizeof p/2;char *strchr();int putchar(\
);while(*q){i+= strchr(p,*q++)-p;if(i>=(int)si zeof p)i-=sizeof p-1;putchar(p[i]\
);}return 0;}

[Keith Thompson]

ok******@gmail. com writes:

I have a situation where , I should keep on reading a FILE stream until
a location. And I have to immediately write the EOF character , so that
the rest of the file is cleared.

EOF is not a character. EOF is a macro that expands to a negative
constant that's used to indicate an end-of-file condition. (That
condition might be indicated by some character on some systems, but
that's system-specific, and is not related to EOF.)

See Ben Pfaff's answer.

--
Keith Thompson (The_Other_Keit h) ks***@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.

[CBFalconer]

ok******@gmail. com wrote:

I have a situation where , I should keep on reading a FILE stream
until a location. And I have to immediately write the EOF character,
so that the rest of the file is cleared.

There is no EOF character. There is only an EOF condition of a
stream. The only portable way to handle your requirement is to
copy the file until you reach the stopping point. Then close both
the file and the new copy.

EOF is a negative int value, not a char value. It is distinct from
all characters. You don't know what it is, but you do know it is
defined in stdio.h. Streams return that value to signal that they
have encountered the end-of-file condition, i.e. there is no more
data.

--
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"Reply" at the bottom of the article headers." - Keith Thompson
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Also see <http://www.safalra.com/special/googlegroupsrep ly/>

[Richard Bos]

CBFalconer <cb********@yah oo.com> wrote:

ok******@gmail. com wrote:

I have a situation where , I should keep on reading a FILE stream
until a location. And I have to immediately write the EOF character,
so that the rest of the file is cleared.

There is no EOF character.

This is not entirely true, which is probably much of the reason for this
confusion.
There _is_ an EOF character in ASCII (and possibly also in other
charsets), but it is only indirectly related to the C EOF macro, and
most definitely does not have the same value[1]. The two should not be
confused, but it's easy for a newbie to do so.

Richard

[1] Because all ASCII characters are zero-or-positive, while EOF < 0.

[CBFalconer]

Richard Bos wrote:

CBFalconer <cb********@yah oo.com> wrote:

ok******@gmail. com wrote:

I have a situation where , I should keep on reading a FILE stream
until a location. And I have to immediately write the EOF character,
so that the rest of the file is cleared.

There is no EOF character.

This is not entirely true, which is probably much of the reason for
this confusion. There _is_ an EOF character in ASCII (and possibly
also in other charsets), but it is only indirectly related to the C
EOF macro, and most definitely does not have the same value[1]. The
two should not be confused, but it's easy for a newbie to do so.

No, there is NO EOF character, especially in ASCII. Some systems
assign some character, or character sequence, to signal EOF. Some
historically popular choices have been:

^Z SUB Who knows why, maybe because the last letter
^D EOT End of Transmission
^Y EM End of medium
^[ ESC Escape
^\ FS File Separator
^] GS Group Separator
^^ RS Record Separator
^_ US Unit Separator

The most commonly used sequences are: CR SUB and CR EOT as seen at
a keyboard. One system used ":EOF" at the immediate head of a line
only, i.e. preceded by CR.

Another generic means of signalling EOF from the keyboard is the
power switch. This one may have undesirable side effects.

--
"The power of the Executive to cast a man into prison without
formulating any charge known to the law, and particularly to
deny him the judgement of his peers, is in the highest degree
odious and is the foundation of all totalitarian government
whether Nazi or Communist." -- W. Churchill, Nov 21, 1943

[Keith Thompson]

CBFalconer <cb********@yah oo.com> writes:

ok******@gmail. com wrote:

I have a situation where , I should keep on reading a FILE stream
until a location. And I have to immediately write the EOF character,
so that the rest of the file is cleared.

There is no EOF character. There is only an EOF condition of a
stream. The only portable way to handle your requirement is to
copy the file until you reach the stopping point. Then close both
the file and the new copy.

EOF is a negative int value, not a char value. It is distinct from
all characters. You don't know what it is, but you do know it is
defined in stdio.h. Streams return that value to signal that they
have encountered the end-of-file condition, i.e. there is no more
data.

One more potential stumbling block: if char is signed, and EOF is,
say, -1, then EOF (or rather the value of what the EOF macro expands
to) *can* be a valid value of type char.

fgetc() and friends return either the value EOF, or a character value
*as an unsigned char converted to int*. A program that incorrectly
stores there result of fgetc() in a char object can mistakenly
interpret valid character data as EOF.

--
Keith Thompson (The_Other_Keit h) ks***@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.

[Barry Schwarz]

On 14 Feb 2006 21:40:46 -0800, ok******@gmail. com wrote:

Hi talents,

I have a situation where , I should keep on reading a FILE stream until
a location. And I have to immediately write the EOF character , so that
the rest of the file is cleared.

Any idea?....

C does not define an EOF character. Some systems define an EOF
character for certain uses (e.g., Windows uses 0x1a as an EOF
character in a text file, but not in a binary one). If your system
supports an EOF character, you would find out about it a newsgroup
that deals specifically with your system.
Remove del for email

[Keith Thompson]

Barry Schwarz <sc******@doezl .net> writes:

On 14 Feb 2006 21:40:46 -0800, ok******@gmail. com wrote:

Hi talents,

I have a situation where , I should keep on reading a FILE stream until
a location. And I have to immediately write the EOF character , so that
the rest of the file is cleared.

Any idea?....

C does not define an EOF character. Some systems define an EOF
character for certain uses (e.g., Windows uses 0x1a as an EOF
character in a text file, but not in a binary one). If your system
supports an EOF character, you would find out about it a newsgroup
that deals specifically with your system.

And even on such systems, writing an EOF character to a file may or
may not do anything useful.

--
Keith Thompson (The_Other_Keit h) ks***@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.

[Richard Bos]

CBFalconer <cb********@yah oo.com> wrote:

Richard Bos wrote:

CBFalconer <cb********@yah oo.com> wrote:

ok******@gmail. com wrote:

I have a situation where , I should keep on reading a FILE stream
until a location. And I have to immediately write the EOF character,
so that the rest of the file is cleared.

There is no EOF character.

This is not entirely true, which is probably much of the reason for
this confusion. There _is_ an EOF character in ASCII (and possibly
also in other charsets), but it is only indirectly related to the C
EOF macro, and most definitely does not have the same value[1]. The
two should not be confused, but it's easy for a newbie to do so.

No, there is NO EOF character, especially in ASCII.

*Goes to look this up*

By the noodly appendages of Cthulhu-in-a-dress, you're right! I never
realised this...

Mind you, it doesn't contradict my point, really; all it does is move me
more firmly into the newbie camp :-/

Richard