mirror of https://github.com/winsw/winsw
28 lines
1.4 KiB
Markdown
28 lines
1.4 KiB
Markdown
# Deferred file operations
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To support self updating services, winsw offers a mechanism to perform file operations before the process you specified in the configuration file gets launched.
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This is often necessary because Windows prevents a file from being overwritten while it's in use.
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To perform file operations, write a text file (in the UTF-8 encoding) at *myapp.copies*
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(that is, it's in the same directory as *myapp.xml* and *myapp.exe* but with a different file extension),
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and for each operation add one line:
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* To move a file, write a line `src>dst`. If the `dst` file already exists it will be overwritten.
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The success or failure of these operations will be recorded in the event log.
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`src` and `dst` should be the full path to file, or you will see failed to copy file.
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example:
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```
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c:\soft\sshd.exe.new>c:\bin\ssh.exe
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```
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Note that it is apparently possible to [rename executables even when it's running](http://superuser.com/questions/488127/why-can-i-rename-a-running-executable-but-not-delete-it), which makes sense if you think about file handles.
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Kohsuke has failed to find any authoritative source of information about this, but experimentally this even works on Windows XP and presumably on all the later Windows versions.
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This behavior can be used to update *WinSW.exe* itself.
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Also see `WINSW_EXECUTABLE` environment variable.
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The `<download>` element in the configuration file also provides an useful building block for a self updating service.
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