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Added a worked example for find

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James Youngman
2007-07-02 08:37:02 +00:00
parent d31d4a4359
commit ea31bc31bb
3 changed files with 49 additions and 3 deletions
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4
ChangeLog
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@@ -59,6 +59,10 @@
* doc/find.texi (Deleting Files): Fixed a typo.
(Deleting Files): Likewise.
New worked example for find.
* doc/find.texi (Copying A Subset of Files): Added a new worked
example.
2007-06-30 Eric Blake <ebb9@byu.net>
* find/pred.c (pred_timewindow): Avoid gcc warnings.

1
NEWS
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@@ -29,6 +29,7 @@ recent findutils release first.
Introduced doc/find-maint.texi, a maintenance manual for findutils.
Added an extra worked example for find (copying a subset of files).
* Major changes in release 4.3.8

47
doc/find.texi
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@@ -3807,9 +3807,9 @@ performed, and compares the different ways of achieving them.
@menu
* Deleting Files::
* Copying A Subset of Files::
* Updating A Timestamp File::
@end menu
@c * Copying A Subset of Files::
@node Deleting Files
@section Deleting Files
@@ -4150,8 +4150,49 @@ portable. The most efficient portable alternative is @samp{-exec
@dots{}+}, but this is insecure and isn't supported by versions of GNU
findutils prior to 4.2.12.
@c @node Copying A Subset of Files
@c @section Copying A Subset of Files
@node Copying A Subset of Files
@section Copying A Subset of Files
Suppose you want to copy some files from @file{/source-dir} to
@file{/dest-dir}, but there are a small number of files in
@file{/source-dir} you don't want to copy.
One option of course is @code{cp /source-dir /dest-dir} followed by
deletion of the unwanted material under @file{/dest-dir}. But often
that can be inconvenient, because for example we would have copied a
large amount of extraneous material, or because @file{/dest-dir} is
too small. Naturally there are many other possible reasons why this
strategy may be unsuitable.
So we need to have some way of identifying which files we want to
copy, and we need to have a way of copying that file list. The second
part of this condition is met by @code{cpio -p}. Of course, we can
identify the files we wish to copy by using @code{find}. Here is a
command that solves our problem:
@example
cd /source-dir
find . -name '.snapshot' -prune -o \( \! -name '*~' -print0 \) |
cpio -pmd0 /dest-dir
@end example
The first part of the @code{find} command here identifies files or
directoires named @file{.snapshot} and tells @code{find} not to
recurse into them (since they do not need to be copied). The
combination @code{-name '.snapshot' -prune} yields false for anything
that didn't get pruned, but it is exactly those files we want to
copy. Therefore we need to use an OR (@samp{-o}) condition to
introduce the rest of our expression. The remainder of the expression
simply arranges for the name of any file not ending in @samp{~} to be
printed.
Using @code{-print0} ensures that white space characters in file names
do not pose a problem. The @code{cpio} command does the actual work
of copying files. The program as a whole fails if the @code{cpio}
program returns nonzero. If the @code{find} command returns non-zero
on the other hand, the Unix shell will not diagnose a problem (since
@code{find} is not the last command in the pipeline).
@node Updating A Timestamp File
@section Updating A Timestamp File