So I have not tried anything yet, but I know those code scripts wont work..
So my though was creating a program wich had some functions ex. rm, delete, mkdir and edit. So all of these programs have something in common, they all have an "exception", like a file name.. So I wondered how the programs actually can handle it, so what I though in the first place was something in an another language, but now what I think it would be in LUA as it is not is this:
Runned in shell: MyProgram run DNS_SERVER
MyProgram
local MyProgramexception = read(MyProgram {$0}:{$1}:{$2})
But it I guess it is not that simple, but what I need is something that run if statements for example like:
public $0 = {exception}
public $1 = {exception}
local run = ({$0}, run)
local del = ({$0}, rm)
local program = ({$1}, dns_server || web_server || other_things..)
This is of course some NON WORKING code as I tried to look as real as possible..
So I wondered if there is someone out there who actually knows this?
Also posted on Arqade, but it was off-topic somehow..
It is a bit a vague question to me (and some vague non-lua code), but I think you mean program arguments, like this:
rename <argument1> <argument2>
To accomplish this, you can store all arguments in a table like this:
local arg = {...}
the ... does the magic. Now, you can access argument #1 by doing this:
arg[1]
I hope I have understood your question well.
Related
I'm almost completely new to Linux programming, and Bash Scripts. I build an amateur radio AllStar node.
I'm trying to create a script that looks at a certain variable and based on that info decides if it should connect or not. I can use a command: asterisk -rx "rpt showvars 47168. This returns a list of variables and their current values. I can store the whole list into a variable that I define, in my test script I just called it MYVAR but I can't seem to only get the value of one of the variables that's listed.
I talked to someone who knows a lot about Linux programming, and she suggested that I try CONNECTED="${MYVAR[3]}" but when I do this, CONNECTED just seems to become a blank variable.
What really frustrates me is I have written programs in other programming languages, and I've been told Bash scripts are easy to learn, but yet I can't seem to get this.
So any help would be great.
how did you assigned your variable?
It seems to me that you want to work with an array, then:
#!/bin/bash
myvar=( $( asterisk -rx "rpt showvars 47168 ) )
echo ${mywar[3]} # this is your fourth element
echo ${#myvar[#]} # this is the total of element in your array
be careful that index in an array starts at 0
I am creating something along the likes of a text adventure game. I have a .yaml file that is my input. This file looks something like this
node_type:
action
title:
Do some stuff
info:
This does some stuff and things
script:
'print("hello world")
print(ret_val)
foo.bar(True)
ret_val = (foo.bar() == True)
if (thing):
print(thing)
print(ret_val)
'
My end goal is to have my python program run the script portion of the yaml file exactly as if it had been copy pasted into the main code. (I know there are about ten bazillion security reasons I should not be running user input like this, but I am the only one writing these nodes, and the only one using this program so I'm mostly just ignoring this fact...)
Currently my attempt goes like this: I load my yaml file as a dict using pyyaml
node = yaml.safe_load(file.yaml)
Then I'm trying to use exec to run my code and hitting a lot of problems, I can't run if statements, I simply get a syntax error, and I can't get any sort of return value from my code. I've tried this as a work around:
def main()
ret_val = "test";
thing = exec(node['script'], globals(),locals())
print(ret_val)
which when run with the above .yaml file prints
>> hello world
>> test
>> True
>> test
for some reason not actually modifying any of my main variables even though I fed them to exec.
Is there any way for me to work around these issues or is there an all together better way to be doing this?
One way of doing this would be to parse the code out and save it to a .py file, from which it can be imported dynamically, for example by importlib.
You might want to encapsulate parsed code into a function, which you can then easily call to invoke your action. Also, it would make sense to specify some default imports there.
I'm working with a growing bash script and within this script I have a number of functions. One of these functions is supposed to return a variables value, but I am running into some issues with the syntax. Below is an example of the code.
ShowTags() {
local tag=0
read tag
echo "$tag"
}
selected_tag=$(ShowTags)
echo "$selected_tag"
pulled this code from a Linux Journal article, but the problem is it doesn't seem to work, or perhaps it does and im missing something. Essentially whenever the function is called the script hangs up and does not output anything, I need to CTRL+C to drop back to CLI.
The article in question is below.
http://www.linuxjournal.com/content/return-values-bash-functions
So my question is this the proper way to return a value? Is there a better or more dependable way of doing this? And if there is please give me an example so I can figure this out without using global variables.
EDIT:
The behavior of this is really getting to me now. I am using the following script.
ShowTags() {
echo "hi"
local tag=0
read tag
echo "$tag"
}
selected_tag=$(ShowTags)
echo "$selected_tag
Basically what happens is bash will act as if the read command is taking place before the echo tag at the top of the function. As soon as I pass something to read though it will run the top echo, and complete the rest of the script. I am not sure why this is happening. This is exactly what is happening in my main script.
Change echo "hi" to echo "hi" >/dev/tty.
The reason you're not seeing it immediately is that $(ShowTags) captures all the standard output of the function, and that gets assigned to selected_tag. So you don't see any of it until you echo that variable.
By redirecting the prompt to /dev/tty, it's always displayed immediately on the terminal, not sent to the function's stdout, so it doesn't get captured by the command substitution.
You are trying to define a function with Name { ... ]. You have to use name() { ... }:
ShowTags() { # add ()
local tag=0
read tag
echo "$tag"
} # End with }
selected_tag=$(ShowTags)
echo "$selected_tag"
It now lets the user type in a string and have it written back:
$ bash myscript
hello world # <- my input
hello world # script's output
You can add a prompt with read -p "Enter tag: " tag to make it more obvious when to write your input.
As #thatotherguy pointed out, your function declaration syntax is off; but I suspect that's a transcription error, as if it was wrong in the script you'd get different problems. I think what's going on is that the read tag command in the function is trying to read a value from standard input (by default that's the terminal), and pausing until you type something in. I'm not sure what it's intended to do, but as written I'd expect it to pause indefinitely until something's typed in.
Solution: either type something in, or use something other than read. You could also add a prompt (read -p "Enter a tag: " tag) to make it more clear what's going on.
BTW, I have a couple of objections to the linux journal article you linked. These aren't relevant to your script, but things you should be aware of.
First, the function keyword is a nonstandard bashism, and I recommend against using it. myfunc() ... is sufficient to introduce a function definition.
Second, and more serious, the article recommends using eval in an unsafe way. Actually, it's really hard to use eval safely (see BashFAQ #48). You can improve it a great deal just by changing the quoting, and even more by not using eval at all:
eval $__resultvar="'$myresult'" # BAD, can evaluate parts of $myresult as executable code
eval $__resultvar='"$myresult"' # better, is only vulnerable to executing $__resultvar
declare $__resultvar="$myresult" # better still
See BashFAQ #6 for more options and discussion.
I am used to object oriented programming. Now, I have just started learning unix bash scripting via linux.
I have a unix script with me. I wanted to break it down into "modules" or preferably programs similar to "more", "ls", etc., and then use pipes to link all my programs together. E.g., "some input" myProg1 | myProg2 | myProg3.
I want to organize my code and make it look neater, instead of all in one script. Also, it will be easy to do testing and development.
Is it possible to do this, especially as a newbie ?
There are a few things you could take a look at, for example the usage of aliases in bash and storing them in either bashrc or a seperate file called by bashrc
that will make running commands easier..
take a look here for expanding commands into aliases (simple aliases are easy)
You can also look into using functions in your code (lots of bash scripts in above link's home folder to make sense of functions browse this site :) which has much better examples...
Take a look here for some piping tails into script
pipe tail output into another script
The thing with bash is its flexibility, so for example if something starts to get too messy for bash you could always write a perl/Java any lang and then call this from within your bash script, capture its output and do something else..
Unsure why all the pipes anyways here is something that may be of help:
./example.sh 20
function one starts with 20
In function 2 20 + 10 = 30
Function three returns 10 + 10 = 40
------------------------------------------------
------------------------------------------------
Local function variables global:
Result2: 30 - Result3: 40 - value2: 10 - value1: 20
The script:
example.sh
#!/bin/bash
input=$1;
source ./shared.sh
one
echo "------------------------------------------------"
echo "------------------------------------------------"
echo "Local function variables global:"
echo "Result2: $result2 - Result3: $result3 - value2: $value2 - value1: $value1"
shared.sh
function one() {
value1=$input
echo "function one starts with $value1"
two;
}
function two() {
value2=10;
result2=$(expr $value1 + $value2)
echo "In function 2 $value1 + $value2 = $result2"
three;
}
function three() {
local value3=10;
result3=$(expr $value2 + $result2;)
echo "Function three returns $value2 + $value3 = $result3"
}
I think the pipes you mean can actually be functions and each function can call one another.. and then you give the script the value which it passes through the functions..
bash is pretty flexible about passing values around, so long as the function being called before has the variable the next function being called by it can reuse it or it can be called from main program
I also split out the functions which can be sourced by another script to carry out the same functions
E2A Thanks for the upvote, I have also decided to include this link
http://tldp.org/LDP/abs/html/sample-bashrc.html
There is an awesome .bashrc to be reused, it has a lot of functions which will also give some insight into how to simplify a lot of daily repetitive commands such as that require piping, an alias can be written to do all of them for you..
You can do one thing.
Just as a C program can be divided into a header file and a source file for reducing complexity, you can divide your bash script into two scripts - a header and a main script but with some differences.
Header file - This will contain all the common variables defined and functions defined which will be used by your main script.
Your script - This will only contain function calls and other logic.You need to use "source <"header-file path">" in your script at starting to get all the functions and variables declared in the header available to your script.
Shell scripts have standard input and output like any other program on Unix, so you can use them in pipes. Splitting your scripts is a good solution because you can later use them in pipes with other commands.
I organize my Bash projects in the following way :
Each command is put in its own file
Reusable functions are kept in a library file which is just a classic script with only functions
All files are in the same directory, so commands can find the library with $(dirname $0)/library
Configuration is stored in another file as environment variables
To keep things clear, you should not use global variables to communicate between functions and main program.
I prepare a template for scripts with the following parts prepared :
Header with name and copyright
Read configuration with source
Load library with source
Check parameters
Function to display help, which is called if asked for or if parameters are wrong
My best advice is : always write the help function, as the next person who will need it is ... yourself !
To install your project you simply copy all files, and explain what to configure in the configuration file.
I've got question about program architecture.
Say you've got 100 different log files with different formats and you need to parse and put that info into an SQL database.
My view of it is like:
use general config file like:
program1->name1("apache",/var/log/apache.log) (modulename,path to logfile1)
program2->name2("exim",/var/log/exim.log) (modulename,path to logfile2)
....
sqldb->configuration
use something like a module (1 file per program) type1.module (regexp, logstructure(somevariables), sql(tables and functions))
fork or thread processes (don't know what is better on Linux now) for different programs.
So question is, is my view of this correct? I should use one module per program (web/MTA/iptablat)
or there is some better way? I think some regexps would be the same, like date/time/ip/url. What to do with that? Or what have I missed?
example: mta exim4 mainlog
2011-04-28 13:16:24 1QFOGm-0005nQ-Ig
<= exim#mydomain.org.ua** H=localhost
(exim.mydomain.org.ua)
[127.0.0.1]:51127 I=[127.0.0.1]:465
P=esmtpsa
X=TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32
CV=no A=plain_server:spam S=763
id=1303985784.4db93e788cb5c#mydomain.org.ua T="test" from
<exim#exim.mydomain.org.ua> for
test#domain.ua
everything that is bold is already parsed and will be putted into sqldb.incoming table. now im having structure in perl to hold every parsed variable like $exim->{timstamp} or $exim->{host}->{ip}
my program will do something like tail -f /file and parse it line by line
Flexability: let say i want to add supprot to apache server (just timestamp userip and file downloaded). all i need to know what logfile to parse, what regexp shoud be and what sql structure should be. So im planning to have this like a module. just fork or thread main process with parameters(logfile,filetype). Maybe further i would add some options what not to parse (maybe some log level is low and you just dont see mutch there)
I would do it like this:
Create a config file that is formatted like this: appname:logpath:logformatname
Create a collection of Perl class that inherit from a base parser class.
Write a script which loads the config file and then loops over its contents, passing each iteration to its appropriate handler object.
If you want an example of steps 1 and 2, we have one on our project. See MT::FileMgr and MT::FileMgr::* here.
The log-monitoring tool wots could do a lot of the heavy lifting for you here. It runs as a daemon, watching as many log files as you could want, running any combination of perl regexes over them and executing something when matches are found.
I would be inclined to modify wots itself (which its licence freely allows) to support a database write method - have a look at its existing handle_* methods.
Most of the hard work has already been done for you, and you can tackle the interesting bits.
I think File::Tail is a nice fit.
You can make an array of File::Tail objects and poll them with select like this:
while (1) {
($nfound,$timeleft,#pending)=
File::Tail::select(undef,undef,undef,$timeout,#files);
unless ($nfound) {
# timeout - do something else here, if you need to
} else {
foreach (#pending) {
# here you can handle log messages depending on filename
print $_->{"input"}." (".localtime(time).") ".$_->read;
}
(from perl File::Tail doc)