In its first form, the command provides the content or the type of an object in the repository. The type is required unless -t or -p is used to find the object type, or -s is used to find the object size, or --textconv or --filters is used (which imply type "blob").
In the second form, a list of objects (separated by linefeeds) is provided on stdin, and the SHA-1, type, and size of each object is printed on stdout. The output format can be overridden using the optional <format> argument. If either --textconv or --filters was specified, the input is expected to list the object names followed by the path name, separated by a single white space, so that the appropriate drivers can be determined.
If -t is specified, one of the <type>.
If -s is specified, the size of the <object> in bytes.
If -e is specified, no output.
If -p is specified, the contents of <object> are pretty-printed.
If <type> is specified, the raw (though uncompressed) contents of the <object> will be returned.
If --batch or --batch-check is given, cat-file will read objects from stdin, one per line, and print information about them. By default, the whole line is considered as an object, as if it were fed to 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:
- The 40-hex object name of the object.
- The type of of the object (the same as cat-file -t reports).
- The size, in bytes, of the object (the same as cat-file -s reports).
- The size, in bytes, that the object takes up on disk. See the note about on-disk sizes in the CAVEATS section below.
- If the object is stored as a delta on-disk, this expands to the 40-hex sha1 of the delta base object. Otherwise, expands to the null sha1 (40 zeroes). See CAVEATS below.
- If this atom is used in the output string, input lines are split at the first whitespace boundary. All characters before that whitespace are considered to be the object name; characters after that first run of whitespace (i.e., the "rest" of the line) are output in place of the %(rest) atom.
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
Whereas --batch-check='%(objectname) %(objecttype)' would produce:
<sha1> SP <type> LF
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
If --follow-symlinks is used, and a symlink in the repository points outside the repository, then cat-file will ignore any custom format and print:
symlink SP <size> LF <symlink> LF
The symlink will either be absolute (beginning with a /), or relative to the tree root. For instance, if dir/link points to ../../foo, then <symlink> will be ../foo. <size> is the size of the symlink in bytes.
If --follow-symlinks is used, the following error messages will be displayed:
<object> SP missing LF
is printed when the initial symlink requested does not exist.
dangling SP <size> LF <object> LF
is printed when the initial symlink exists, but something that it (transitive-of) points to does not.
loop SP <size> LF <object> LF
is printed for symlink loops (or any symlinks that require more than 40 link resolutions to resolve).
notdir SP <size> LF <object> LF
is printed when, during symlink resolution, a file is used as a directory name.
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 or delta base will be reported.