Complex statement

[seema_coma@yahoo.co.in]

Hi all,

Can somebody explain what this statement does,
if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)

Thanks in advance
Seema

[manoj1978@gmail.com]

Re: Complex statement


seema_coma@yaho o.co.in wrote:[color=blue]
> Hi all,
>
> Can somebody explain what this statement does,
> if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)
>
> Thanks in advance
> Seema[/color]

tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL);
if (tempFD < 0)

Do "man open" to see open's input parameters and return value.

[Martin Ambuhl]

Re: Complex statement

seema_coma@yaho o.co.in wrote:[color=blue]
> Hi all,
>
> Can somebody explain what this statement does,
> if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)[/color]

If we knew for sure what version of what library you were using, some
might. But they shouldn't, since the experts for your platform or
implementation have newsgroups of their own. Unless your question is
about C as defined by the standard, no reliable substantive answers from
comp.lang.c should be expected. In your case, the function open() is
not defined as part of the standard C libaries (nor are O_RDWR, O_CREAT,
or O_EXCL). Questions about fopen(), a standard C function, we can
answer. It is most likely (although definitely not certain) that one of
the unix programming newsgroups is what you want.

[John Bode]

Re: Complex statement


seema_coma@yaho o.co.in wrote:[color=blue]
> Hi all,
>
> Can somebody explain what this statement does,
> if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)
>
> Thanks in advance
> Seema[/color]

The open() function itself is not part of the standard C library, but
part of the Unix (POSIX?) API. Refer to the man page for specifics.
The above is a shorthand equivalent to the following:

char *tempFileName = ...; /* some file name */
int fileAccessMask = 0_RDWR | O_CREAT | O_EXCL;
int tempFD = open (tempFileName, fileAccessMask) ;

if (tempFD < 0)
{
/* do something */
}

Essentially, the open() call and the test are being squashed into the
conditional expression.

[tedu]

Re: Complex statement

John Bode wrote:[color=blue]
> seema_coma@yaho o.co.in wrote:[color=green]
> > Hi all,
> >
> > Can somebody explain what this statement does,
> > if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)
> >
> > Thanks in advance
> > Seema[/color]
>
> The open() function itself is not part of the standard C library, but
> part of the Unix (POSIX?) API. Refer to the man page for specifics.
> The above is a shorthand equivalent to the following:
>
> char *tempFileName = ...; /* some file name */
> int fileAccessMask = 0_RDWR | O_CREAT | O_EXCL;
> int tempFD = open (tempFileName, fileAccessMask) ;[/color]

OT, but you should never call open with O_CREAT and no mode.

[Anonymous 7843]

Re: Complex statement

In article <1125660780.124 997.93420@z14g2 000cwz.googlegr oups.com>,
John Bode <john_bode@my-deja.com> wrote:[color=blue]
>
> char *tempFileName = ...; /* some file name */
> int fileAccessMask = 0_RDWR | O_CREAT | O_EXCL;[/color]

gcc says: invalid suffix "_RDWR" on integer constant

[kernelxu@hotmail.com]

Re: Complex statement

seema_c...@yaho o.co.in wrote:[color=blue]
> Can somebody explain what this statement does,
>if ((tempFD = open(tempFileNa me, O_RDWR | O_CREAT | O_EXCL)) < 0)[/color]

open() is not a standard C function, it belongs to UNIX.
if calling open() failed, it will return -1.
therfore, the expression " (tempFD = open(tempFileNa me, O_RDWR |
O_CREAT | O_EXCL)) < 0" is to check whether the call is successful or
not.