bsd/man/man2/close.2

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  34 .\"     @(#)close.2     8.2 (Berkeley) 4/19/94
  35 .\"
  36 .Dd April 19, 1994
  37 .Dt CLOSE 2
  38 .Os BSD 4
  39 .Sh NAME
  40 .Nm close
  41 .Nd delete a descriptor
  42 .Sh SYNOPSIS
  43 .Fd #include <unistd.h>
  44 .Ft int
  45 .Fn close "int d"
  46 .Sh DESCRIPTION
  47 The
  48 .Fn close
  49 call deletes a descriptor from the per-process object
  50 reference table.
  51 If this is the last reference to the underlying object, the
  52 object will be deactivated.
  53 For example, on the last close of a file
  54 the current
  55 .Em seek
  56 pointer associated with the file is lost;
  57 on the last close of a
  58 .Xr socket 2
  59 associated naming information and queued data are discarded;
  60 on the last close of a file holding an advisory lock
  61 the lock is released (see further
  62 .Xr flock 2 ) .
  63 .Pp
  64 When a process exits,
  65 all associated file descriptors are freed, but since there is
  66 a limit on active descriptors per processes, the
  67 .Fn close
  68 function call
  69 is useful when a large quantity of file descriptors are being handled.
  70 .Pp
  71 When a process forks (see
  72 .Xr fork 2 ) ,
  73 all descriptors for the new child process reference the same
  74 objects as they did in the parent before the fork.
  75 If a new process is then to be run using
  76 .Xr execve 2 ,
  77 the process would normally inherit these descriptors.  Most
  78 of the descriptors can be rearranged with
  79 .Xr dup2 2
  80 or deleted with
  81 .Fn close
  82 before the
  83 .Xr execve
  84 is attempted, but if some of these descriptors will still
  85 be needed if the execve fails, it is necessary to arrange for them
  86 to be closed if the execve succeeds.
  87 For this reason, the call
  88 .Dq Li fcntl(d, F_SETFD, 1)
  89 is provided,
  90 which arranges that a descriptor will be closed after a successful
  91 execve; the call
  92 .Dq Li fcntl(d, F_SETFD, 0)
  93 restores the default,
  94 which is to not close the descriptor.
  95 .Sh RETURN VALUES
  96 Upon successful completion, a value of 0 is returned.
  97 Otherwise, a value of -1 is returned and the global integer variable
  98 .Va errno
  99 is set to indicate the error.
 100 .Sh ERRORS
 101 .Fn Close
 102 will fail if:
 103 .Bl -tag -width Er
 104 .It Bq Er EBADF
 105 .Fa D
 106 is not an active descriptor.
 107 .It Bq Er EINTR
 108 An interrupt was received.
 109 .El
 110 .Sh SEE ALSO
 111 .Xr accept 2 ,
 112 .Xr flock 2 ,
 113 .Xr open 2 ,
 114 .Xr pipe 2 ,
 115 .Xr socket 2 ,
 116 .Xr socketpair 2 ,
 117 .Xr execve 2 ,
 118 .Xr fcntl 2
 119 .Sh STANDARDS
 120 .Fn Close
 121 conforms to
 122 .St -p1003.1-88 .