| 1 | .\" Copyright (c) 1980 Regents of the University of California.
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| 2 | .\" All rights reserved. The Berkeley software License Agreement
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| 3 | .\" specifies the terms and conditions for redistribution.
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| 4 | .\"
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| 5 | .\" @(#)close.2 6.3 (Berkeley) 5/22/86
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| 6 | .\"
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| 7 | .TH CLOSE 2 "May 22, 1986"
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| 8 | .UC 4
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| 9 | .SH NAME
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| 10 | close \- delete a descriptor
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| 11 | .SH SYNOPSIS
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| 12 | .nf
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| 13 | .ft B
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| 14 | #include <unistd.h>
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| 15 |
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| 16 | int close(int \fId\fP)
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| 17 | .ft R
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| 18 | .fi
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| 19 | .SH DESCRIPTION
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| 20 | The
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| 21 | .B close
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| 22 | call deletes a descriptor from the per-process object
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| 23 | reference table.
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| 24 | If this is the last reference to the underlying object, then
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| 25 | it will be deactivated.
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| 26 | For example, on the last close of a file
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| 27 | the current \fIseek\fP pointer associated with the file is lost;
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| 28 | on the last close of a TCP/IP descriptor
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| 29 | associated naming information and queued data are discarded;
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| 30 | on the last close of a file holding an advisory lock
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| 31 | the lock is released (see further
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| 32 | .BR fcntl (2)).
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| 33 | .PP
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| 34 | A close of all of a process's descriptors is automatic on
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| 35 | .IR exit ,
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| 36 | but since
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| 37 | there is a limit on the number of active descriptors per process,
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| 38 | .B close
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| 39 | is necessary for programs that deal with many descriptors.
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| 40 | .PP
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| 41 | When a process forks (see
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| 42 | .BR fork (2)),
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| 43 | all descriptors for the new child process reference the same
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| 44 | objects as they did in the parent before the fork.
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| 45 | If a new process is then to be run using
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| 46 | .BR execve (2),
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| 47 | the process would normally inherit these descriptors. Most
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| 48 | of the descriptors can be rearranged with
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| 49 | .BR dup2 (2)
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| 50 | or deleted with
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| 51 | .B close
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| 52 | before the
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| 53 | .B execve
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| 54 | is attempted, but if some of these descriptors will still
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| 55 | be needed if the
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| 56 | .B execve
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| 57 | fails, it is necessary to arrange for them to be closed if the
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| 58 | .B execve
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| 59 | succeeds.
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| 60 | For this reason, the call ``fcntl(d, F_SETFD, \fIflags\fR)'' is provided,
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| 61 | that can be used to mark a descriptor "close on exec" by setting
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| 62 | the
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| 63 | .B FD_CLOEXEC
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| 64 | flag:
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| 65 | .PP
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| 66 | .RS
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| 67 | fcntl(d, F_SETFD, fcntl(d, F_GETFD) | FD_CLOEXEC);
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| 68 | .RE
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| 69 | .SH "RETURN VALUE
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| 70 | Upon successful completion, a value of 0 is returned.
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| 71 | Otherwise, a value of \-1 is returned and the global integer variable
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| 72 | .B errno
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| 73 | is set to indicate the error.
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| 74 | .SH ERRORS
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| 75 | .B Close
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| 76 | will fail if:
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| 77 | .TP 15
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| 78 | [EBADF]
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| 79 | \fID\fP is not an active descriptor.
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| 80 | .SH "SEE ALSO"
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| 81 | .BR open (2),
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| 82 | .BR pipe (2),
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| 83 | .BR execve (2),
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| 84 | .BR fcntl (2).
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