bug#11809: document "So how do we just simply make a backup file?"
Jim Meyering wrote:
> Bernhard Voelker wrote:
>> On 06/29/2012 10:48 AM, Jim Meyering wrote:
>>> Here's the doc patch I suggested, but I'll hold off for now.
>>> I'd like to hear if anyone thinks it's worth adding a new option,
>>> which would obviate such a script.
>>
>> I think it's okay, that special backup case is described in the info
>> page of cp twice anyway.
>>
>>> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
>>> index 08ef2d8..5207c44 100644
>>> --- a/doc/coreutils.texi
>>> +++ b/doc/coreutils.texi
>>> @@ -7675,9 +7675,11 @@ cp invocation
>>> #!/bin/sh
>>> # Usage: backup FILE...
>>> # Create a @sc{gnu}-style backup of each listed FILE.
>>> +fail=0
>>> for i; do
>>> - cp --backup --force -- "$i" "$i"
>>> + cp --backup --force -- "$i" "$i" || fail=1
>>> done
>>> +exit $fail
>>> @end example
>>>
>>> @item --copy-contents
>>
>> When we speak of "backup", then maybe "--preserve=all" would be nice.
>>
>> BTW: that special backup case accepts -a which includes both -d and -R
>> which both are maybe not ideal if you speak about a backup of a regular
>> file. The former treats symlinks specially, and the latter is designed
>> to recurse into directories - both may be misleading (although -d may
>> make some sense in certain situation when creating a backup of a
>> symlink). WDYT?
>
> Adding --preserve=all sounds like a good idea.
> Thanks.
>
> Allowing this little script to work also for non-regular files
> seems like it'd be useful, too. But it's beginning to look as if
> this combination of options is both useful and involved enough that
> the functionality should be provided by a new --only-backup option.
I went ahead and pushed this:
>From 5f6c22fceedd0d350e1a8246d4d73840de666c7e Mon Sep 17 00:00:00 2001
From: Jim Meyering
Date: Fri, 29 Jun 2012 10:45:31 +0200
Subject: [PATCH] doc: improve sample backup script
* doc/coreutils.texi (cp invocation): Make the backup script exit
with an accurate reflection of any failure.
Also, add --preserve=all.
Improved-by: Bernhard Voelker
---
doc/coreutils.texi | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 08ef2d8..954a1f8 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7675,9 +7675,11 @@ cp invocation
#!/bin/sh
# Usage: backup FILE...
# Create a @sc{gnu}-style backup of each listed FILE.
+fail=0
for i; do
- cp --backup --force -- "$i" "$i"
+ cp --backup --force --preserve=all -- "$i" "$i" || fail=1
done
+exit $fail
@end example
@item --copy-contents
--
1.7.11.1.104.ge7b44f1
bug#11809: document "So how do we just simply make a backup file?"
On 06/29/2012 10:48 AM, Jim Meyering wrote:
> Here's the doc patch I suggested, but I'll hold off for now.
> I'd like to hear if anyone thinks it's worth adding a new option,
> which would obviate such a script.
I think it's okay, that special backup case is described in the info
page of cp twice anyway.
> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
> index 08ef2d8..5207c44 100644
> --- a/doc/coreutils.texi
> +++ b/doc/coreutils.texi
> @@ -7675,9 +7675,11 @@ cp invocation
> #!/bin/sh
> # Usage: backup FILE...
> # Create a @sc{gnu}-style backup of each listed FILE.
> +fail=0
> for i; do
> - cp --backup --force -- "$i" "$i"
> + cp --backup --force -- "$i" "$i" || fail=1
> done
> +exit $fail
> @end example
>
> @item --copy-contents
When we speak of "backup", then maybe "--preserve=all" would be nice.
BTW: that special backup case accepts -a which includes both -d and -R
which both are maybe not ideal if you speak about a backup of a regular
file. The former treats symlinks specially, and the latter is designed
to recurse into directories - both may be misleading (although -d may
make some sense in certain situation when creating a backup of a
symlink). WDYT?
Have a nice day,
Berny
bug#11809: document "So how do we just simply make a backup file?"
Bernhard Voelker wrote:
> On 06/29/2012 10:48 AM, Jim Meyering wrote:
>> Here's the doc patch I suggested, but I'll hold off for now.
>> I'd like to hear if anyone thinks it's worth adding a new option,
>> which would obviate such a script.
>
> I think it's okay, that special backup case is described in the info
> page of cp twice anyway.
>
>> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
>> index 08ef2d8..5207c44 100644
>> --- a/doc/coreutils.texi
>> +++ b/doc/coreutils.texi
>> @@ -7675,9 +7675,11 @@ cp invocation
>> #!/bin/sh
>> # Usage: backup FILE...
>> # Create a @sc{gnu}-style backup of each listed FILE.
>> +fail=0
>> for i; do
>> - cp --backup --force -- "$i" "$i"
>> + cp --backup --force -- "$i" "$i" || fail=1
>> done
>> +exit $fail
>> @end example
>>
>> @item --copy-contents
>
> When we speak of "backup", then maybe "--preserve=all" would be nice.
>
> BTW: that special backup case accepts -a which includes both -d and -R
> which both are maybe not ideal if you speak about a backup of a regular
> file. The former treats symlinks specially, and the latter is designed
> to recurse into directories - both may be misleading (although -d may
> make some sense in certain situation when creating a backup of a
> symlink). WDYT?
Adding --preserve=all sounds like a good idea.
Thanks.
Allowing this little script to work also for non-regular files
seems like it'd be useful, too. But it's beginning to look as if
this combination of options is both useful and involved enough that
the functionality should be provided by a new --only-backup option.
bug#11809: document "So how do we just simply make a backup file?"
Jim Meyering wrote:
> jida...@jidanni.org wrote:
>> (info "(coreutils) Backup options") should add some examples, for
>> "So how do we make a backup file of m?"
>> $ ls
>> m
>> $ cp -b m m #no go
>
> Thanks for the suggestion.
> I use this zsh/bash shell function:
>
> backup ()
> {
> local i
> for i in "$@"; do
> command cp -bf "$i" "$i"
> done
> }
>
> but as I inserted the above, I realize it's buggy.
> It doesn't propagate failure like you'd expect,
> so here's a better one:
>
> backup()
> {
> local i fail=0
> for i in "$@"; do
> command cp -bf -- "$i" "$i" || fail=1
> done
> return $fail
> }
>
> That's already almost what info coreutils says:
>
> Make a backup of each file that would otherwise be overwritten or removed.
> As a special case, @command{cp} makes a backup of @var{source} when the
> force
> and backup options are given and @var{source} and @var{dest} are the same
> name for an existing, regular file. One useful application of this
> combination of options is this tiny Bourne shell script:
>
> @example
> #!/bin/sh
> # Usage: backup FILE...
> # Create a @sc{gnu}-style backup of each listed FILE.
> for i; do
> cp --backup --force -- "$i" "$i"
> done
> @end example
>
> I'll adjust that to reflect the above improvement:
> Do you think that's enough?
Here's the doc patch I suggested, but I'll hold off for now.
I'd like to hear if anyone thinks it's worth adding a new option,
which would obviate such a script.
>From 3a1bc89c3e3ca277be49d4fceb60abb57e3fc9d2 Mon Sep 17 00:00:00 2001
From: Jim Meyering
Date: Fri, 29 Jun 2012 10:45:31 +0200
Subject: [PATCH] doc: improve sample backup script
* doc/coreutils.texi (cp invocation): Make the backup script exit
with an accurate reflection of any failure.
---
doc/coreutils.texi | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 08ef2d8..5207c44 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -7675,9 +7675,11 @@ cp invocation
#!/bin/sh
# Usage: backup FILE...
# Create a @sc{gnu}-style backup of each listed FILE.
+fail=0
for i; do
- cp --backup --force -- "$i" "$i"
+ cp --backup --force -- "$i" "$i" || fail=1
done
+exit $fail
@end example
@item --copy-contents
--
1.7.11.1.59.gbc9e7dd
bug#11809: document "So how do we just simply make a backup file?"
JM> I deliberately restricted the "make backup only" functionality to the JM> very limited case that is documented. Well you had better explicitly document that it does not work with all forms in the cp SYNOPSIS, else people will think it is broken...
bug#11809: document "So how do we just simply make a backup file?"
jida...@jidanni.org wrote: > OK but (info "(coreutils) Backup options") should also link back to the exact > cp -b spot, else most folks will miss it. > > P.S., There _is_ an easier way of making backups of several files, > But there is a bug, one has to do it one at a time despite -b. Bug bug bug. > > $ \cp -fb h k l . > cp: `h' and `./h' are the same file > cp: `k' and `./k' are the same file > cp: `l' and `./l' are the same file > $ \cp -fb h h > $ No, that was deliberate. I deliberately restricted the "make backup only" functionality to the very limited case that is documented. Widening the semantics, as you suggest above, seems like it would make this "feature" more likely to be discovered accidentally -- with data loss, when both originals and backups are removed. If people think the make-backup-only feature is useful enough for multiple files, then we can consider adding an --only-backup option, (better name welcome, but it cannot start with "--backup") rather than co-opting the --force --backup combination and requiring a script to process more than one at a time.
bug#11809: document "So how do we just simply make a backup file?"
OK but (info "(coreutils) Backup options") should also link back to the exact cp -b spot, else most folks will miss it. P.S., There _is_ an easier way of making backups of several files, But there is a bug, one has to do it one at a time despite -b. Bug bug bug. $ \cp -fb h k l . cp: `h' and `./h' are the same file cp: `k' and `./k' are the same file cp: `l' and `./l' are the same file $ \cp -fb h h $
bug#11809: document "So how do we just simply make a backup file?"
jida...@jidanni.org wrote:
> (info "(coreutils) Backup options") should add some examples, for
> "So how do we make a backup file of m?"
> $ ls
> m
> $ cp -b m m #no go
Thanks for the suggestion.
I use this zsh/bash shell function:
backup ()
{
local i
for i in "$@"; do
command cp -bf "$i" "$i"
done
}
but as I inserted the above, I realize it's buggy.
It doesn't propagate failure like you'd expect,
so here's a better one:
backup()
{
local i fail=0
for i in "$@"; do
command cp -bf -- "$i" "$i" || fail=1
done
return $fail
}
That's already almost what info coreutils says:
Make a backup of each file that would otherwise be overwritten or removed.
As a special case, @command{cp} makes a backup of @var{source} when the force
and backup options are given and @var{source} and @var{dest} are the same
name for an existing, regular file. One useful application of this
combination of options is this tiny Bourne shell script:
@example
#!/bin/sh
# Usage: backup FILE...
# Create a @sc{gnu}-style backup of each listed FILE.
for i; do
cp --backup --force -- "$i" "$i"
done
@end example
I'll adjust that to reflect the above improvement:
Do you think that's enough?
> $ cp m n
> $ mv -b n m
bug#11809: document "So how do we just simply make a backup file?"
(info "(coreutils) Backup options") should add some examples, for "So how do we make a backup file of m?" $ ls m $ cp -b m m #no go $ cp m n $ mv -b n m
