LuaPosix

Lua Posix

This is a list of the Lua Posix functions. Included is helpful snippets of code. Install lua posix. To get this list do:

require "posix"
for a in pairs(posix) do 
  print(a)
end

access

check real user's permissions for a file

SYNOPSIS

posix.access(pathname, mode)

DESCRIPTION

access() checks whether the calling process can access the file pathname. If pathname is a symbolic link, it is dereferenced.

The mode specifies the accessibility check(s) to be performed, and is either the string "f", or one or more of "r", "w", and "x". "f" tests for the existence of the file. "r", "w", and "x" test whether the file exists and grants read, write, and execute permissions, respectively.

RETURN VALUES

On success (all requested permissions granted), zero is returned. On error (at least one char in mode asked for a permission that is denied, or some other error occurred), nil, errorstr and errno is returned.

require "posix"
status, errstr, errno = posix.access("/etc/passwd", "rw")

Reference: http://swoolley.org/man.cgi/access

chdir

INPUT

• Path - where do you want to change directory to

OUPUT

• 0 if success
  • nil if failed

bar = require "posix"
bar.chdir("/etc/")
--print(bar.getcwd()) to see where you are

0 if success, nil if failure. If you

print(bar.chdir("/var/lob"))
-- it will print the system error message also
nil     /var/lob: No such file or directory     2

The access function returns three values altogether; the following example may help to distinguish their use:

lpos = require "posix"
ptr, msg, code = lpos.access("/etc/dhcp")
if ptr == nil then
  print("msg  = " .. msg)
  print("code = " .. code)
else
  print("ptr  = " .. ptr)
end

chmod

INPUT

• PATH - where is the file or directory
  • MODE - what mode to you want to change on the file

OUPUT

• string - 0 if sucess, nil failure

bar = require "posix"
bar.chmod("/etc/passwd", "a=rwx")
--looks like you need to use the ugoa format for this, not numbers

chown

INPUT

• Path-location of file or directory
• UID - User id number
• GID - Group id number

OUPUT

• String - 0 is success and nil for failure

bar = require "posix"
print(bar.chown("/etc/passwd",100,200)
--above will give back nil. Since we printed it will also give back the system errors.

ctermid

INPUT

• NONE- DISPLAYS the terminal id

OUTPUT

• String with the terminal id

bar = require "posix"
print(bar.ctermid())

dir

Directory listing INPUT

• PATH - directory

OUTPUT

• TABLE - table with the file name contents of the directory
  • Failure returns a nil value

bar = require "posix"
bobo = bar.dir("/var/log")
for a,b in ipairs(bobo) do print(b) end
-- the bobo table will output all the file names in /var/log/

errno

Display the error information

INPUT

• NONE

OUPUT

• Success, or Error message

bar = require "posix"
a,b = bar.dir("/var/foo"), bar.errno()
print(a,b)
-- a will be nil or 0, b will be No such file or directory or Success

exec

Replaces the running process with the command specified. Command line arguments are given as additional arguments. (To start a sub process, you probably want fork+exec, not just exec.)

INPUT

• PATH-Location of binary
• ARGs-options to pass to binary

OUTPUT

• Strings

bar = require "posix"
bobo = bar.exec("/bin/ls", "-l", "/etc/")

files

Returns an interator function that loops over each file in the given directory

INPUT

• PATH- Directory

OUPUT

require "posix"

for name in posix.files("/etc") do
    print (name)
end

fork

INPUT

• None

OUTPUT returns: -1 on error, 0 to the child process, and the pid of the child to the parent.

require("posix")

print ("parent: my pid is: " .. posix.getpid("pid")) 

local pid = posix.fork () 

if ( pid == -1 ) then
        print ("parent: The fork failed.")
elseif ( pid == 0 ) then
        print ("child: Hello World! I am pid: " .. posix.getpid("pid") )
        print ("child: I'll sleep for 1 second ... ")
        posix.sleep(1)
        print ("child: Good bye");
else
        print ("parent: While the child sleeps, I'm still running.")
        print ("parent: waiting for child (pid:" .. pid .. ") to die...")
        posix.wait(pid)
        print ("parent: child died, but I'm still alive.")
        print ("parent: Good bye")
end

parent: my pid is: 11050
child: Hello World! I am pid: 11051
child: I'll sleep for 1 second ... 
parent: While the child sleeps, I'm still running.
parent: waiting for child (pid:11051) to die...
child: Good bye
parent: child died, but I'm still alive.
parent: Good bye

getcwd

INPUT

• NONE

OUTPUT

• String- contents of which is the current working directory

bar = require "posix"
print(bar.getcwd())

getenv

INPUT

• NONE

OUPUT

• Table - Current Environment settings

bar = require "posix"
bobo = bar.getenv()
for a,b in pairs(bobo) do print(b) end
-- Varible - Value

getgroup

INPUT

• GID, or groupname

OUPUT

• TABLE -contents of which hold the group name,gid, and users

bar = require "posix"
bobo = bar.getgroup(1000)
for a,b in pairs(bobo) do print(a,b) end
--if you use pairs then bobo will print also the name and gid or the group
--if you use ipairs then just the group members
1 user1
2 user2
name wheel
gid 1

getlogin

Couldn't get it to work

INPUT

• NONE

OUPUT

• UNKNOWN

getpassword

INPUT

• NAME or UID

OUPUT

• TABLE- values from /etc/passwd

uid,name,gid,password,gecos,dir,shell

bar = require "posix"
bobo = bar.getpasswd("root")
for a,b in pairs(bobo) do print(a,b) end
--uid 0
--name root
--gid 0
--passwd x
--gecos root
--dir /root/
--shell /bin/bash

getprocessid

INPUT

• Selector - either [egid,euid,gid,uid,pgrp,pid,ppid,NULL]

OUPUT

• Number that matches the current process and the selector

bar = require "posix"
print(bar.getprocessid("gid"))
18456 
--it just printed the current process id for the script or interactive lua.

Is there a version difference here? AL 1.7.7 calls this "getpid" Nangel

kill

INPUT

• PID- process identifier
• Signal- to send to the process

OUPUT

bar = require "posix"
--kill your current process
bobo = bar.getprocessid("pid")
bar.kill(bobo,9)
---Signals looks to be the number signals accepted in Unix

link

Hard Links INPUT

• Oldpath-
• Newpath-

'OUTPUT If you want output 0 sucess, nil errors

bar = require "posix"
bobo = bar.link("/etc/passwd", "testfile")
-- 0 for success, nil for errors

mkdir

INPUT

• PATH-path to new dir

OUTPUT If you are looking for output-

• 0 for success
• nil for failure

bar = require "posix"
bar.mkdir("/home/user/bobo")
--set the above to a variable to get output

mkfifo

INPUT

• PATH- where to make the fifo

wait

---

If you are using this under linux also get