to apply the filter to the content recorded in the index at <path>.
--batch::
- Print the SHA-1, type, size, and contents of each object provided on
- stdin. May not be combined with any other options or arguments.
+--batch=<format>::
+ Print object information and contents for each object provided
+ on stdin. May not be combined with any other options or arguments.
+ See the section `BATCH OUTPUT` below for details.
--batch-check::
- Print the SHA-1, type, and size of each object provided on stdin. May not
- be combined with any other options or arguments.
+--batch-check=<format>::
+ Print object information for each object provided on stdin. May
+ not be combined with any other options or arguments. See the
+ section `BATCH OUTPUT` below for details.
OUTPUT
------
If <type> is specified, the raw (though uncompressed) contents of the <object>
will be returned.
-If '--batch' is specified, output of the following form is printed for each
-object specified on stdin:
+BATCH OUTPUT
+------------
+
+If `--batch` or `--batch-check` is given, `cat-file` will read objects
+from stdin, one per line, and print information about them.
+
+Each line is considered as a whole object name, and is parsed as if
+given to linkgit:git-rev-parse[1].
+
+You can specify the information shown for each object by using a custom
+`<format>`. The `<format>` is copied literally to stdout for each
+object, with placeholders of the form `%(atom)` expanded, followed by a
+newline. The available atoms are:
+
+`objectname`::
+ The 40-hex object name of the object.
+
+`objecttype`::
+ The type of of the object (the same as `cat-file -t` reports).
+
+`objectsize`::
+ The size, in bytes, of the object (the same as `cat-file -s`
+ reports).
+
+`objectsize:disk`::
+ The size, in bytes, that the object takes up on disk. See the
+ note about on-disk sizes in the `CAVEATS` section below.
+
+If no format is specified, the default format is `%(objectname)
+%(objecttype) %(objectsize)`.
+
+If `--batch` is specified, the object information is followed by the
+object contents (consisting of `%(objectsize)` bytes), followed by a
+newline.
+
+For example, `--batch` without a custom format would produce:
------------
<sha1> SP <type> SP <size> LF
<contents> LF
------------
-If '--batch-check' is specified, output of the following form is printed for
-each object specified on stdin:
+Whereas `--batch-check='%(objectname) %(objecttype)'` would produce:
------------
-<sha1> SP <type> SP <size> LF
+<sha1> SP <type> LF
------------
-For both '--batch' and '--batch-check', output of the following form is printed
-for each object specified on stdin that does not exist in the repository:
+If a name is specified on stdin that cannot be resolved to an object in
+the repository, then `cat-file` will ignore any custom format and print:
------------
<object> SP missing LF
------------
+
+CAVEATS
+-------
+
+Note that the sizes of objects on disk are reported accurately, but care
+should be taken in drawing conclusions about which refs or objects are
+responsible for disk usage. The size of a packed non-delta object may be
+much larger than the size of objects which delta against it, but the
+choice of which object is the base and which is the delta is arbitrary
+and is subject to change during a repack. Note also that multiple copies
+of an object may be present in the object database; in this case, it is
+undefined which copy's size will be reported.
+
+
GIT
---
Part of the linkgit:git[1] suite