Data

Tools

Indexes

Applications

Experiments

Awesome

An open API service indexing awesome lists of open source software.

https://github.com/dtxdf/appscript

Very lightweight script to create self-extractable archives
https://github.com/dtxdf/appscript

Last synced: 20 days ago
JSON representation

Very lightweight script to create self-extractable archives

Awesome Lists containing this project

README 

          
NAME

     appscript - Simple, lightweight and effective tool for creating SFX files



SYNOPSIS

     appscript -v

     appscript [-L] [-a arch] [-c algo] [-o filename] [-S sysroot] directory



DESCRIPTION

     appscript is a very lightweight and easy-to-use tool for creating self-

     extracting executables.



     From the developer's perspective, tar(1) is used to compress a directory

     into a tarball, known as the "payload," which is stored in the .rodata

     section, objcopy(1) to convert the payload into a valid elf(3) object

     file, and then clang(1) to compile the payload with the C-written stub.

     And from the user's perspective, it just need to run the executable file,

     and the magic happens behind the scenes: the AppScript (the SFX file)

     reads the addresses where the payload is located and uses libarchive(3)

     to extract the files to a temporary directory, finally executing an

     executable file named APPSCRIPT. The user can pass any environment

     variables and arguments to the AppScript, and the APPSCRIPT executable

     can handle them just like any other program or script.



     However, an AppScript does much more than what has been described above.

     First, it sets handlers for SIGHUP, SIGINT, SIGQUIT, SIGTERM, SIGXCPU,

     and SIGXFSZ to stop the AppScript when it's running.  SIGALRM, SIGVTALRM,

     SIGPROF, SIGUSR1, and SIGUSR2 are ignored. Next, it checks if the

     /var/tmp/appscript directory exists and, if so, uses it to create

     temporary directories; otherwise, /tmp is used as fallback. The reason

     /var/tmp/appscript is preferred is that a system administrator can

     configure this location to mount a tmpfs(4) filesystem to improve the

     performance of very large AppScripts. This is more secure than setting

     "vfs.usermount=1" and letting the user (or, in this case, the user's

     process) mount a tmpfs(4) filesystem. Regardless of the directory used,

     it must have file mode 1777; otherwise, an EX_NOPERM error will be

     returned. After initial checks, the tarball is extracted to a temporary

     location determined by the directories mentioned above.  The AppScript

     will refuse to extract absolute paths and entries containing periods, and

     will apply basic protection against symbolic links (see

     ARCHIVE_EXTRACT_SECURE_SYMLINKS in archive_write_disk(3) for details).

     Finally, if no signal is received and no errors are detected during the

     files extraction, the AppScript will attempt to execute the APPSCRIPT

     file. For this to succeed, the file must have the execute bit set and the

     owner must be the same as the effective uid, which should be the case

     since the uid and gid are changed to the caller when the files are

     extracted. As a final task, the temporary directory is recursively

     removed in a similar way to the -r and -f flags in rm(1).



     -L   All symbolic links will be followed.

	  Normally, symbolic links are archived as such. With this option, the

	  target of the link will be archived instead.



     -s   Tells the linker to create a statically linked executable.



     -v   Display version information about appscript.



     -a arch

	  Specifies an architecture for the binary other than the default,

	  which is the same as the host. Valid arguments are: amd64, aarch64,

	  armv7, i386, riscv64, powerpc, powerpc64, and powerpc64le.



     -c algo

	  Compression algorithm to be used to compress the directory. Valid

	  arguments: gzip, xz, and zstd. The default is zstd.



     -o filename

	  Name of the resulting executable. By default, a.AppScript.



     -S sysroot

	  Tells clang(1) to use a specified directory as the logical root

	  directory for resolving system headers and libraries.



	  By default, when no argument is specified, it uses the

	  %%PREFIX%%/freebsd-sysroot/arch directory only if it exists;

	  otherwise, it falls back to /. If you have installed the

	  arch-freebsd-sysroot package, this should work correctly, but this

	  parameter is primarily necessary when you need to cross-compile a

	  statically linked binary.



     directory

	  Directory to be compressed.



	  appscript assumes that the APPSCRIPT script is already present and

	  has the execute bit set.



ENVIRONMENT

     APPSCRIPT_PWD

	  Since APPSCRIPT runs from the current user's working directory, it

	  does not know the location of the temporary directory. This

	  environment variable specifies that location.



     APPSCRIPT_SCRIPT

	  Absolute path to the AppScript that is currently running.



EXAMPLES

   Improving performance

     If you are the sovereign of your system, users will appreciate you if you

     enable tmpfs(4) at /var/tmp/appscript for very large AppScripts:



	   # /etc/fstab

	   tmpfs   /var/tmp/appscript  tmpfs   rw,size=1G,mode=1777,late  0   0



     Then:



	   # mkdir -p /var/tmp/appscript

	   # mount /var/tmp/appscript



   The "Hello World" example

     To create the most basic AppScript all you have to do is create a

     directory:



	   $ mkdir hello-world



     Create the APPSCRIPT file:



	   $ cat << EOF > ./hello-world/APPSCRIPT

	   #!/bin/sh



	   echo "Hello, world!"

	   EOF



     And set the execute bit:



	   $ chmod +x ./hello-world/APPSCRIPT



     To finally create the AppScript:



	   $ appscript ./hello-world

	   $ ls

	   ./a.AppScript

	   $ ./a.AppScript

	   Hello, world!



SEE ALSO

     tar(1) libarchive(3) signal(3) sysexits(3)



AUTHORS

     Jesus Daniel Colmenares Oviedo