close(2) [minix man page]

CLOSE(2)							System Calls Manual							  CLOSE(2)

NAME

       close - delete a descriptor

SYNOPSIS

       #include <unistd.h>

       int close(int d)

DESCRIPTION

       The  close  call deletes a descriptor from the per-process object reference table.  If this is the last reference to the underlying object,
       then it will be deactivated.  For example, on the last close of a file the current seek pointer associated with the file is  lost;  on  the
       last close of a TCP/IP descriptor associated naming information and queued data are discarded; on the last close of a file holding an advi-
       sory lock the lock is released (see further fcntl(2)).

       A close of all of a process's descriptors is automatic on exit, but since there is a limit on the number of active descriptors per process,
       close is necessary for programs that deal with many descriptors.

       When  a	process forks (see fork(2)), all descriptors for the new child process reference the same objects as they did in the parent before
       the fork.  If a new process is then to be run using execve(2), the process would normally inherit these descriptors.  Most of the  descrip-
       tors  can  be  rearranged with dup2(2) or deleted with close before the execve is attempted, but if some of these descriptors will still be
       needed if the execve fails, it is necessary to arrange for them to be closed if the execve succeeds.  For this reason, the call	``fcntl(d,
       F_SETFD, flags)'' is provided, that can be used to mark a descriptor "close on exec" by setting the FD_CLOEXEC flag:

	      fcntl(d, F_SETFD, fcntl(d, F_GETFD) | FD_CLOEXEC);

RETURN VALUE

       Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and the global integer variable errno is set to
       indicate the error.

ERRORS

       Close will fail if:

       [EBADF]	      D is not an active descriptor.

SEE ALSO

       open(2), pipe(2), execve(2), fcntl(2).

4th Berkeley Distribution					   May 22, 1986 							  CLOSE(2)

Check Out this Related Man Page

DUP(2)								System Calls Manual							    DUP(2)

NAME

       dup, dup2 - duplicate a descriptor

SYNOPSIS

       #include <unistd.h>

       int dup(int oldd)
       int dup2(int oldd, int newd)

DESCRIPTION

       Dup  duplicates	an existing descriptor.  The argument oldd is a small non-negative integer index in the per-process descriptor table.  The
       value must be less than OPEN_MAX, the size of the table.  The new descriptor returned by the call, let's name it newd, is the  lowest  num-
       bered descriptor that is not currently in use by the process.

       The  object referenced by the descriptor does not distinguish between references using oldd and newd in any way.  Thus if newd and oldd are
       duplicate references to an open file, read(2), write(2) and lseek(2) calls all move a single pointer into the file, and append  mode,  non-
       blocking  I/O  and asynchronous I/O options are shared between the references.  If a separate pointer into the file is desired, a different
       object reference to the file must be obtained by issuing an additional open(2) call.  The close-on-exec flag on the new file descriptor	is
       unset.

       In  the	second	form  of  the call, the value of newd desired is specified.  If this descriptor is already in use, the descriptor is first
       deallocated as if a close(2) call had been done first.  Newd is not closed if it equals oldd.

RETURN VALUE

       The value -1 is returned if an error occurs in either call.  The external variable errno indicates the cause of the error.

ERRORS

       Dup and dup2 fail if:

       [EBADF]	      Oldd or newd is not a valid active descriptor

       [EMFILE]       Too many descriptors are active.

NOTES

       Dup and dup2 are now implemented using the F_DUPFD function of fcntl(2), although the old system call interfaces still exist to support old
       programs.

SEE ALSO

       open(2), close(2), fcntl(2), pipe(2).

4th Berkeley Distribution					   May 13, 1986 							    DUP(2)

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close(2) [minix man page]

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