1IO::AtomicFile(3)     User Contributed Perl Documentation    IO::AtomicFile(3)
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NAME

6       IO::AtomicFile - write a file which is updated atomically
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SYNOPSIS

9           use strict;
10           use warnings;
11           use feature 'say';
12           use IO::AtomicFile;
13
14           # Write a temp file, and have it install itself when closed:
15           my $fh = IO::AtomicFile->open("bar.dat", "w");
16           $fh->say("Hello!");
17           $fh->close || die "couldn't install atomic file: $!";
18
19           # Write a temp file, but delete it before it gets installed:
20           my $fh = IO::AtomicFile->open("bar.dat", "w");
21           $fh->say("Hello!");
22           $fh->delete;
23
24           # Write a temp file, but neither install it nor delete it:
25           my $fh = IO::AtomicFile->open("bar.dat", "w");
26           $fh->say("Hello!");
27           $fh->detach;
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DESCRIPTION

30       This module is intended for people who need to update files reliably in
31       the face of unexpected program termination.
32
33       For example, you generally don't want to be halfway in the middle of
34       writing /etc/passwd and have your program terminate!  Even the act of
35       writing a single scalar to a filehandle is not atomic.
36
37       But this module gives you true atomic updates, via "rename".  When you
38       open a file /foo/bar.dat via this module, you are actually opening a
39       temporary file /foo/bar.dat..TMP, and writing your output there. The
40       act of closing this file (either explicitly via "close", or implicitly
41       via the destruction of the object) will cause "rename" to be called...
42       therefore, from the point of view of the outside world, the file's
43       contents are updated in a single time quantum.
44
45       To ensure that problems do not go undetected, the "close" method done
46       by the destructor will raise a fatal exception if the "rename" fails.
47       The explicit "close" just returns "undef".
48
49       You can also decide at any point to trash the file you've been
50       building.
51

METHODS

53       IO::AtomicFile inherits all methods from IO::File and implements the
54       following new ones.
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56   close
57           $fh->close();
58
59       This method calls its parent "close" in IO::File and then renames its
60       temporary file as the original file name.
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62   delete
63           $fh->delete();
64
65       This method calls its parent "close" in IO::File and then deletes the
66       temporary file.
67
68   detach
69           $fh->detach();
70
71       This method calls its parent "close" in IO::File. Unlike "delete" in
72       IO::AtomicFile it does not then delete the temporary file.
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AUTHOR

75       Eryq (eryq@zeegee.com).  President, ZeeGee Software Inc
76       (http://www.zeegee.com).
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CONTRIBUTORS

79       Dianne Skoll (dfs@roaringpenguin.com).
80

82       Copyright (c) 1997 Erik (Eryq) Dorfman, ZeeGee Software, Inc. All
83       rights reserved.
84
85       This program is free software; you can redistribute it and/or modify it
86       under the same terms as Perl itself.
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90perl v5.32.0                      2020-07-28                 IO::AtomicFile(3)
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