Luachild is a lua module to spawn system processes and perform basic communication with them, i.e. pipes and environment variables set. It is compatible with lua 5.3 and luajit 2.1 and it works under windows and any os with posix spawn+environ api (e.g. linux).
The code was extracted from the LuaDist Ex module. Very few modification were made, so the original license (MIT) was kept, Copyright 2007 Mark Edgar.
If you need a legal statement for these changes, please refer to the Unlicense text in the COPYING.txt file. It also applies to any file without any explicit distribution statement.
A luarocks specs file is provided, so it is possible to build luachild using the command line
luarocks make
In test.lua there is an example of how to use the module. However, the following code uses most of the API:
local lc = require 'luachild'
local env_dump = ''
for k,v in pairs(lc.environ()) do
env_dump = env_dump .. ' ' .. k .. '=' .. v .. '\n'
end
lc.setenv("ENV_DUMP", env_dump)
local r,w = lc.pipe()
local p = lc.spawn { 'lua', '-e', 'print(os.getenv("ENV_DUMP"))', stdout = w }
p:wait()
w:close()
print(r:read('*l'))
For a quick reference:
local lc = require 'luachild' will load the module. After that you will be
able to access to the functions described in the following.
local e = lc.environ() will return a table containing all the environment
variables.
lc.setenv(name, value) will set the value of the environment variable name
to value. Both the arguments must be a string. Value can also be nil, in
which case the variable will be unset. Note: after this function call,
lc.environ() and any child process will get the new value for the variable,
but os.getenv will not. This is because lua follows the standard C definition
of the getenv function.
local r,w = lc.pipe() will return the two sides of a pipe. You can use r
and w as normal files: what you write in w will be read in r
local process = lc.spawn { 'cmd', 'arg1', 'arg2'} create a new process
running the command cmd with argument arg1, arg2 and so on. The only
argument to lc.spawn is a table so you can pass some additional option as
key/value pair. The stdin, stdout and stderr fields can contain file
descriptors to/from which redirect the output/input. It can be a standard file
returned by io.open or one of the two result of lc.pipe(). The env field
can contain a table that describe the environment variables to be set for the
new process. It must be a string-to-string map, and if missing the current env will
be used (the same one returned by lc.environ()). The returned value can be
converted to string to get some information about the sub-process.
lc.wait(process) or process:wait() will wait for the end of the process. It
will return the integer returned by the process.
In the standard C, the command parameters are zero-terminated strings. So it is not possible to pass '\0' in a command line parameter to a subprocess.
Moreover, under the Windows platform, the spawn function uses the
CreateProcess API. It will expand the filesystem wildcard characters '* ' and
'?' . So it is not possible to pass these charaters to the subprocess.
Similar modules are: