doc: document the apply-default-acl algorithm.

[apply-default-acl.git] / doc / man / apply-default-acl.1

diff --git a/doc/man/apply-default-acl.1 b/doc/man/apply-default-acl.1
index d8d66948f7acf569ea7cdb4588c94ac5201e1d39..e6a67995dc23e929b1ae2269075bb70e53453314 100644 (file)
--- a/doc/man/apply-default-acl.1
+++ b/doc/man/apply-default-acl.1
@@ -34,3 +34,82 @@ contents of \fBfoo\fR are processed.
 Apply the default ACL literally; that is, don't use a heuristic to
 decide whether or not to mask the execute bit. This usually results in
 looser-than-necessary execute permissions.
+
+.SH ALGORITHM
+.IP "I. Argument validation" 0.4i
+.RS
+.IP "a. If any part of the target path contains a symlink" 0.4i
+Return failure
+.IP "b. If there's no default ACL to apply"
+Return success
+.IP "c. If the target is not a (non-hardlink) regular file or directory"
+Return failure
+.RE
+.IP "II. ACL application"
+.RS
+.IP "a. If the target is a directory" 0.4i
+Set the target's default ACL equal to its parent's default ACL
+.IP "b. Set the target's access ACL equal to its parent's default ACL"
+.IP "c. If the target is a directory"
+Return success
+.IP "d. If the target was executable by anyone"
+Return success
+.IP "e. If \fB--no-exec-mask\fR was given"
+Return success
+.IP "f. Unset the user/group/other/mask execute bits"
+.IP "g. Return success"
+.RE
+.P
+The action of apply-default ACL largely mimics what the kernel would
+do if you ran \fImkdir\fR or \fItouch\fR to create a new file. The one
+point of disagreement is on how to mask group-execute permissions for
+files. The kernel will let the \(dqmask\(dq bits prevent group-execute,
+whereas apply-default-acl will explicitly remove the group-execute bits.
+For example,
+
+.nf
+.I $ mkdir herp
+.I $ setfacl --default --modify user:mjo:rw herp
+.I $ touch herp/derp
+.I $ getfacl --omit-header herp/derp
+user::rw-
+user:mjo:rw-
+group::r-x                     #effective:r--
+mask::rw-
+other::r--
+.fi
+
+In the same situation, apply-default-acl will mask the group \fBx\fR bit:
+
+.nf
+.I $ apply-default-acl herp/derp
+.I $ getfacl --omit-header herp/derp
+user::rw-
+user:mjo:rw-
+group::r--
+mask::rw-
+other::r--
+.fi
+
+The author is of the opinion that the latter is more sensible, if not
+simply more consistent.
+
+.SH EXIT CODE
+.P
+When given a single path, the following codes correspond directly to
+the action of the program on that path:
+.IP \fB0\ (EXIT_SUCCESS)\fR
+Success
+.IP \fB1\ (EXIT_FAILURE)\fR
+Failure due to a symlink, hardlink, or invalid/inaccessible path
+.IP \fB2\fP
+Other unexpected library error
+.P
+When called on multiple paths, the results from all paths are
+collected and the \(dqworst\(dq result is returned. For example, if
+one path succeeds and another fails, the overall result will be
+failure. If one succeeds, one fails, and one causes an error, then the
+overall result will be an error; and so on.
+.P
+When the \fB\-\-recursive\fR flag is used, the exit code is computed
+as if all affected paths were passed, depth-first, on the command-line.