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6.8 Operating Only on New Files
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The '--after-date=DATE' ('--newer=DATE', '-N DATE') option causes 'tar'
to only work on files whose data modification or status change times are
newer than the DATE given. If DATE starts with '/' or '.', it is taken
to be a file name; the data modification time of that file is used as
the date. If you use this option when creating or appending to an
archive, the archive will only include new files. If you use
'--after-date' when extracting an archive, 'tar' will only extract files
newer than the DATE you specify.
If you only want 'tar' to make the date comparison based on
modification of the file's data (rather than status changes), then use
the '--newer-mtime=DATE' option.
You may use these options with any operation. Note that these
options differ from the '--update' ('-u') operation in that they allow
you to specify a particular date against which 'tar' can compare when
deciding whether or not to archive the files.
'--after-date=DATE'
'--newer=DATE'
'-N DATE'
Only store files newer than DATE.
Acts on files only if their data modification or status change
times are later than DATE. Use in conjunction with any operation.
If DATE starts with '/' or '.', it is taken to be a file name; the
data modification time of that file is used as the date.
'--newer-mtime=DATE'
Acts like '--after-date', but only looks at data modification
times.
These options limit 'tar' to operate only on files which have been
modified after the date specified. A file's status is considered to
have changed if its contents have been modified, or if its owner,
permissions, and so forth, have been changed. (For more information on
how to specify a date, see Date input formats; remember that the
entire date argument must be quoted if it contains any spaces.)
Gurus would say that '--after-date' tests both the data modification
time ('mtime', the time the contents of the file were last modified) and
the status change time ('ctime', the time the file's status was last
changed: owner, permissions, etc.) fields, while '--newer-mtime' tests
only the 'mtime' field.
To be precise, '--after-date' checks _both_ 'mtime' and 'ctime' and
processes the file if either one is more recent than DATE, while
'--newer-mtime' only checks 'mtime' and disregards 'ctime'. Neither
does it use 'atime' (the last time the contents of the file were looked
at).
Date specifiers can have embedded spaces. Because of this, you may
need to quote date arguments to keep the shell from parsing them as
separate arguments. For example, the following command will add to the
archive all the files modified less than two days ago:
$ tar -cf foo.tar --newer-mtime '2 days ago'
verbose tutorial::) GNU 'tar' will try to convert the specified date
back to its textual representation and compare that with the one given
with the option. If the two dates differ, 'tar' will print a warning
saying what date it will use. This is to help user ensure he is using
the right date. For example:
$ tar -c -f archive.tar --after-date='10 days ago' .
tar: Option --after-date: Treating date `10 days ago' as 2006-06-11
13:19:37.232434
*Please Note:* '--after-date' and '--newer-mtime' should not be
used for incremental backups. Incremental Dumps, for
proper way of creating incremental backups.
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