@hackage arx0.2.2

SYNOPSIS arx (-h | -[?] | --help) arx (-v | --version) arx shdat (-b )? (-o

)? < input arx shdat (-b )? (-o

)? + arx tmpx <option,archive>* (//+ (//+ <option,archive>*)?)?

DESCRIPTION A UNIX executable is a simple thing -- a file the kernel can execute, one way or another, via an interpreter or directly as object code. Every executable induces a family of executions -- instances of execu- tion with different command line arguments, with different files in the working directory and with different environment variables present.

   The  arx  tool captures the parameters of an execution and encodes them
   as an executable, making for easy, consistent transfer  and  repetition
   of  a  particular  run.  The generated executable ensures that each run
   occurs in a  freshly  allocated  temporary  directory,  with  only  the
   desired  files  in  scope;  it uses traps to ensure the cleanup of this
   directory; and its format is a simple POSIX shell  script,  relying  on
   just a few shell tools.

DEPENDENCIES The arx tool relies on the presence of sed, tr, date, head, tar, hex- dump and sh. When unpacking tar archives, it may use the -j or -z (bzip2 and gzip, respectively) options of tar. Scripts have been tested with dash and the GNU tools as well as the sh implementation and user- land tools that are part of busybox.

APPLICATION The tmpx subcommand of arx offers a variety of options for bundling code and a task to run. The shdat subcommand exposes the lower-level functionality of encoding binary data in a shell script that outputs that binary data, using HERE documents and some odd replacement rules for nulls.

   Scripts generated by tmpx and shdat may be fed to sh over STDIN to exe-
   cute them. This can be helpful when using ssh and sudo  to  set  up  an
   execution context; for example:

   arx tmpx ... | ssh user@host.com sudo sh

   Scripts  generated  by  tmpx will pass their arguments to the contained
   script or command. To pass arguments when piping to sh, use -s:

   arx tmpx ... | ssh user@host.com sudo sh -s a b c

   Some arguments to the  generated  script  will  be  treated  specially,
   namely,  --extract,  --no-rm  and  --no-run.  Please see the section on
   Passing Arguments, below, for more information about these options.

ARX COMMANDLINE PROCESSING For all subcommands, when options overlap in their effect -- for exam- ple, setting the output with -o -- the rightmost option takes prece- dence. Whenever -h, -? or --help is present on the command line, help is displayed and the program exits.

   When  paths  are  specified on an arx command line, they must be quali-
   fied, starting with /, ./ or ../. This simplifies the command line syn-
   tax, overall, without introducing troublesome ambiguities.

TMPX The tmpx subcommand bundles together archives, environment settings and an executable or shell command in to a Bourne-compatible script that runs the command or executable in a temporary directory, after having unpacked the archives and set the environment.

   Any number of file path arguments may be specified; they will be inter-
   preted  as  tar  archives  to include in bundled script. If - is given,
   then STDIN will be included as an archive stream. If no  arguments  are
   given,  it is assumed that no archives are desired and only the command
   and environment are bundled.

   The temporary directory created by the script  is  different  for  each
   invocation,  with a name of the form /tmp/tmpx-<timestamp>-<randomhex>.
   The timestamp format is %Y.%m.%dT%H.%M.%SZ, in UTC.  One  happy  conse-
   quence  of  this  is that earlier jobs sort ASCIIbetically before later
   jobs. After execution, the temporary  directory  is  removed  (or  not,
   depending on the -rm[10!_] family of options).

      -rm0, -rm1, -rm_, -rm!
             By  default,  the  temporary  directory created by the script
             will be deleted no matter the exit status status of the task.
             These options cause a script to be generated that deletes the
             temporary directory only on success, only on failure,  always
             (the default) or never.

      -b <size>
             Please  see  the  documentation  for this option, shared with
             shdat, below.

      -o <path>
             By default, the generated script is sent to STDOUT. With  -o,
             output is redirected to the given path.

      -e <path>
             Causes  the  file  specified to be packaged as the task to be
             run. A binary executable, a Ruby script or  a  longish  shell
             script all fit here.

   In  addition to these options, arguments of the form VAR=VALUE are rec-
   ognized as environment mappings and stored away in the  script,  to  be
   sourced on execution.

   Without  -e,  the tmpx subcommand tries to find the task to be run as a
   sequence of arguments delimited by a  run  of  slashes.  The  following
   forms are all recognized:

   arx tmpx  ...some args... // ...command...
   arx tmpx  ...some args... // ...command... // ...more args...
   arx tmpx // ...command... // ...some args...

   The  slash  runs  must  have the same number of slashes and must be the
   longest continuous runs of slashes on the  command  line.  The  command
   will be included as-is in a Bourne shell script.

SHDAT The shdat subcommand translates binary data in to a shell script which outputs the binary data. The data is encoded in HERE documents in such a way that data without NULs is not changed and that data with NULs is minimally expanded: about 1% for randomish data like compressed tar- balls and about 10% in pathological cases.

   The  shdat  subcommand  can be given any number of paths, which will be
   concatenated in the order given. If no path is given, or if - is given,
   then STDIN will be read.

      -b <size>
             The  size  of data chunks to place in each HERE document. The
             argument is a positive integer followed by suffixes  like  B,
             K,  KiB,  M and MiB, in the manner of dd, head and many other
             tools. The default is 4MiB.  This is unlikely to make a  dif-
             ference for you unless the generated script is intended to be
             run on a memory-constrained system.

      -o <path>
             By default, the generated script is sent to STDOUT. With  -o,
             output is redirected to the given path.

EXAMPLES # Installer script that preserves failed builds. git archive HEAD | bzip2 | arx tmpx -rm0 - // make install > go.sh # Now install as root; but don't log in as root. cat ./go.sh | ssh joey@hostname sudo /bin/sh

   # Variation of the above.
   git archive HEAD | bzip2 | arx tmpx -rm0 - -e ./build-script.py > go.sh

   # Bundle an instance of an application with DB credentials and run it.
   arx tmpx -rm! ./app.tbz ./stage-info.tgz // rake start | ssh ...

   # Get dump of linking info for build that works here but not there.
   arx tmpx ./server-build.tgz LD_DEBUG=files // ./bin/start | ssh ...

   # Test out Cabal source distribution of this package:
   arx tmpx // 'cd arx-* && cabal configure && cabal build' // \
            -rm0 ./dist/arx-0.0.0.tar.gz | sh

PASSING ARGUMENTS TO GENERATED SCRIPTS The scripts generated by tmpx treat some arguments as special, internal options, to allow for inspecting them should there be a need to deter- mine their contents.

      --extract
             Unpack the data in the present directory and do nothing else.

      --no-rm
             Run the script as normal but do not delete the generated tem-
             porary directory.

      --no-run
             Unpack  into  a  temporary directory as normal but do not run
             the user's command.

   To prevent arguments from being specially treated, use // in the  argu-
   ment list:

   a-tmpx-script.sh --no-rm // a b c --extract

   In the above example, --extract will be passed to the inner command, in
   the same way as a, b, c. The following example causes ab, c and --no-rm
   to be printed one after another, each on their own line.

   arx tmpx // printf "'%s\n'" '"$@"' | sh -s // ab c --no-rm

NOTES The timestamp is not the common ISO 8601 format, %Y-%m-%dT%H:%M:%SZ, because of software and build processes that attach special meaning to colons in pathnames.

BUGS The command line parser offers no hints or help of any kind; it fails with the simple message "argument error". The two most common mistakes I make are:

   o Not qualifying paths with /, ./ or ../.

   o Not specifying a subcommand (tmpx or shdat).