svnlook is a tool provided by Subversion for examining the various revisions and transactions in a repository. No part of this program attempts to change the repository—it's a “read-only” tool. svnlook is typically used by the repository hooks for reporting the changes that are about to be committed (in the case of the pre-commit hook) or that were just committed (in the case of the post-commit hook) to the repository. A repository administrator may use this tool for diagnostic purposes.

svnlook has a straightforward syntax:

$ svnlook help
general usage: svnlook SUBCOMMAND REPOS_PATH [ARGS & OPTIONS ...]
Note: any subcommand which takes the '--revision' and '--transaction'
      options will, if invoked without one of those options, act on
      the repository's youngest revision.
Type "svnlook help <subcommand>" for help on a specific subcommand.
…

Nearly every one of svnlook 's subcommands can operate on either a revision or a transaction tree, printing information about the tree itself, or how it differs from the previous revision of the repository. You use the --revision and --transaction options to specify which revision or transaction, respectively, to examine. Note that while revision numbers appear as natural numbers, transaction names are alphanumeric strings. Keep in mind that the filesystem only allows browsing of uncommitted transactions (transactions that have not resulted in a new revision). Most repositories will have no such transactions, because transactions are usually either committed (which disqualifies them from viewing) or aborted and removed.

In the absence of both the --revision and --transaction options, svnlook will examine the youngest (or “HEAD”) revision in the repository. So the following two commands do exactly the same thing when 19 is the youngest revision in the repository located at /path/to/repos:

$ svnlook info /path/to/repos
$ svnlook info /path/to/repos --revision 19

The only exception to these rules about subcommands is the svnlook youngest subcommand, which takes no options, and simply prints out the HEAD revision number.

$ svnlook youngest /path/to/repos
19

Output from svnlook is designed to be both human- and machine-parsable. Take as an example the output of the info subcommand:

$ svnlook info /path/to/repos
sally
2002-11-04 09:29:13 -0600 (Mon, 04 Nov 2002)
27
Added the usual
Greek tree.

The output of the info subcommand is defined as:

This output is human-readable, meaning items like the datestamp are displayed using a textual representation instead of something more obscure (such as the number of nanoseconds since the Tasty Freeze guy drove by). But this output is also machine-parsable—because the log message can contain multiple lines and be unbounded in length, svnlook provides the length of that message before the message itself. This allows scripts and other wrappers around this command to make intelligent decisions about the log message, such as how much memory to allocate for the message, or at least how many bytes to skip in the event that this output is not the last bit of data in the stream.

Another common use of svnlook is to actually view the contents of a revision or transaction tree. The svnlook tree command displays the directories and files in the requested tree. If you supply the --show-ids option, it will also show the filesystem node revision IDs for each of those paths (which is generally of more use to developers than to users).

$ svnlook tree /path/to/repos --show-ids
/ <0.0.1>
 A/ <2.0.1>
  B/ <4.0.1>
   lambda <5.0.1>
   E/ <6.0.1>
    alpha <7.0.1>
    beta <8.0.1>
   F/ <9.0.1>
  mu <3.0.1>
  C/ <a.0.1>
  D/ <b.0.1>
   gamma <c.0.1>
   G/ <d.0.1>
    pi <e.0.1>
    rho <f.0.1>
    tau <g.0.1>
   H/ <h.0.1>
    chi <i.0.1>
    omega <k.0.1>
    psi <j.0.1>
 iota <1.0.1>

Once you've seen the layout of directories and files in your tree, you can use commands like svnlook cat , svnlook propget , and svnlook proplist to dig into the details of those files and directories.

svnlook can perform a variety of other queries, displaying subsets of bits of information we've mentioned previously, reporting which paths were modified in a given revision or transaction, showing textual and property differences made to files and directories, and so on. The following is a brief description of the current list of subcommands accepted by svnlook , and the output of those subcommands: