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G'day,
I've tried to come up with ways to execute commands without leaving
scripts open to shell-special syntax hacks.
I've created my own value-added "PosixExec" pseudo-module (actually,
just a single Lua executable script that can go with, and probably
should be wrapped up as, a LuaRocks item). It builds on luaposix,
especially subprocess-spawn facilities, such as dup2(), pipe(),
fork(), setenv(), cwd(), glob(), and ultimately execp().
The parent then uses poll(), read(), write() and, finally, wait()
to work with child stdin/stdout/stderr, receiving "hup" signal from
the I/O streams and to get final exit status.
The PosixExec script is a value-added version of the fork() example
in luaposix.
---
You can find it used extensively in my "lglicua" SourceForge project,
where I use it as a shim for many things, e.g. "apt-get".
The general invocation is:
local PE = require("PosixExec")
local Result
Result = PE.exec_quietly("ls", {"-al"})
PE.ValidateRun(Result)
The first parameter, a string, is found (or not) using the shell's
PATH; the remaining arguments are untouched (although an extra
Options item brings file globbing back into play, for one argument
only).
Both "PE.exec" and "PE.exec_quietly" return a Result table,
which especially errno is inspected by ValidateRun:
return {
stdout = table.concat(ThisExec.FDs[fd1].Output),
stderr = table.concat(ThisExec.FDs[fd2].Output),
errno = DemiseErrno,
errstr = DemiseErrstr,
Command = Command,
}
An extra Options table on the exec* calls lets you do thing like:
- Set the working directory (cd) for the command;
- Merge child's stderr (fd[2]) into stdout(fd1) at the
child's level, so the streams are synchronous, not
asynchronous (similar to the shell's "2>&1" file
redirection);
- Set a list of environment to (optional) values, e.g.:
{
{"LC_ALL", "C"},
}
- Nominate various parameter(s) for Shell-style file
globbing, as this is one of the things deliberately
disabled, but which is still very useful for some
commands.
---
You can get PosixExec from the following lglicua tarball (earlier
releases than -alpha6 might have fewer features):
https://sourceforge.net/projects/lglicua/files/lglicua-0.1-alpha6.tar.gz/download
---
I have only tried PosixExec under GNU/Linux because:
(a) That was what lglicua was all about; and
(b) I don't have a workable Windows installation to use.
---
Hope this helps,
sur-behoffski (Brenton Hoff)
programmer, Grouse Software