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-- Additions to the posix module (of luaposix).

module ("posix", package.seeall)

--- Run a program like <code>os.system</code>, but without a shell.

-- @param file filename of program to run

-- @param ... arguments to the program

-- @return status exit code, or nil if fork or wait fails

-- @return error message, or exit type if wait succeeds

function system (file, ...)

local pid = fork ()

if pid == 0 then

return execp (file, ...)

else

local pid, reason, status = wait (pid)

return status, reason -- If wait failed, status is nil & reason is error

end

end

--- Check permissions like <code>access</code>, but for euid.

-- Based on the glibc function of the same name. Does not always check

-- for read-only file system, text busy, etc., and does not work with

-- ACLs &c.

-- @param file file to check

-- @param mode checks to perform (as for access)

-- @return 0 if access allowed; <code>nil</code> otherwise (and errno is set)

function euidaccess (file, mode)

local pid = getpid ()

if pid.uid == pid.euid and pid.gid == pid.egid then

-- If we are not set-uid or set-gid, access does the same.

return access (file, mode)

end

local stats = stat (file)

if not stats then

return

end

-- The super-user can read and write any file, and execute any file

-- that anyone can execute.

if pid.euid == 0 and ((not string.match (mode, "x")) or

string.match (stats.st_mode, "x")) then

return 0

end

-- Convert to simple list of modes.

mode = string.gsub (mode, "[^rwx]", "")

if mode == "" then

return 0 -- The file exists.

end

-- Get the modes we need.

local granted = stats.st_mode:sub (1, 3)

if pid.euid == stats.st_uid then

granted = stats.st_mode:sub (7, 9)

elseif pid.egid == stats.st_gid or set.new (getgroups ()):member(stats.st_gid) then

granted = stats.st_mode:sub (4, 6)

end

granted = string.gsub (granted, "[^rwx]", "")

if string.gsub ("[^" .. granted .. "]", mode) == "" then

return 0

end

set_errno (EACCESS)

end