I am writing scripts in tcl for a project I am working on.
I wanted to automate things as much as possible and wanted to not touch the source code of the script as far as possible. I want to run the main script file from a .bat or .job file sort of thing where I pass the command to execute the script along with the arguments.
I have referred to this post on stackoverflow:
How to run tcl script in other tcl script?
And have done pretty much the same thing. However, since my script is naked code rather than a single huge proc, I dont have the "args" parameter to read the arguments I wanted to pass.
For example, if script1.tcl is the main file containing the naked code, I want a file script2.job or script2.bat such that,
<command-to-run-script1.tcl> <mandatory-args> <optional-args>
is the content of the file.
Any suggestions on how I can implement the same?
To run a Tcl script, passing in some arguments, do:
tclsh script1.tcl theFirstArgument theSecondArgument ...
That's how it works in CMD scripts/BAT files on Windows, and in shell scripts on all Unixes. You might want to put quotes around some of the arguments too, but that's just absolute normal running of a program with arguments. (The tclsh might need to be tclsh8.5 or tclsh85 or … well, it depends on how it's installed. And script1.tcl might need to be a full path to the script.)
Inside the script, the arguments (starting at theFirstArgument) will appear in the Tcl list in the global argv variable. Note that this is not args, which is a feature of procedures. There are lots of ways of parsing the list of arguments, but any quoting supplied during the call itself should have been already stripped.
Here's a very simple version:
foreach argument $argv {
puts "Oh, I seem to have a >>$argument<<"
}
You probably need something more elaborate! There's many possibilities though, so be sure to be exact to get more focussed ideas.
If you're calling Tcl from another Tcl script, you need to use exec to do it. On the other hand, you can make things a bit easier for yourself in other ways:
exec [info nameofexecutable] script1.tcl theFirstArgument theSecondArgument ...
The info nameofexecutable command returns the name of the Tcl interpreter program (often tclsh8.5 or wish86 or …)
Related
This is related to u-boot.
I looked at this link (How to test the return of a command in U-Boot CLI) but it doesn't cover what I need. I also checked some other pages related to the 'test' command in u-boot but I can't figure out how to do what I would like. So there it is.
I have a u-boot command on a SBC which returns a set of information as text printed on the screen, where some part are strings representing versions. What I would like is to check whether the command return contains some specific strings to choose automatically what to do.
I have seen a few 'test' command help, but I couldn't figure out how to do this type of check on the text returned by this command. My goal is to have a set of nested ifs to choose in the different cases, or anything equivalent. If regex can be used, they perhaps could be helpful.
Does anybody know how to do this?
Thank you.
In U-Boot's hush shell there is no support for pipes. There is also no command like grep. So there are no means to succeed via U-Boot's built-in shell commands.
If you have access to the source of the command that you are executing, you could change it and use function env_set() to write the relevant data to environment variables and then use test for your purposes.
When trying to use the r or run commands in lldb I get an error like this: error: shell expansion failed (reason: invalid JSON). consider launching with 'process launch'.
It works when I just use process launch but I really do not feel like doing that.
Is there any way I could make either an alias or make shell expansions not fail?
The way lldb does shell expansion is to run a little tool called lldb-argdumper (it is in Xcode.app/Contents/SharedFrameworks/LLDB.framework/Resources on macOS) with the command arguments that you passed. lldb-argdumper wraps the contents of argv as JSON, and writes that to stdout. lldb then parses the JSON back into args and inserts the args one by oneinto the argc/argv array when it launches the process.
Something in the output is not getting properly wrapped. You can probably see what it is by looking at the output of lldb-argdumper with your arguments. Whatever it is, it's a bug, so if you can reproduce it please file with your example with http://bugs.llvm.org.
(lldb) command alias run-no-shell process launch -X 0 --
will produce an alias that doesn't do shell expansion. You can also put this in your ~/.lldbinit.
I ran into this recently. TL;DR: make sure your shell does not echo anything during initialization. Run <your-shell> -c date to confirm; only the date should be printed.
The problem was that my shell's initialization file was echoing some stuff, which was getting prepended to lldb-argdumper's JSON output. (lldb doesn't run lldb-argdumper directly; it invokes your default shell to run lldb-argdumper.)
Specifically, I use fish as my shell, which does not have separate initialization paths for interactive and non-interactive sessions. (See this issue for discussion of whether this is good.) bash and zsh have separate init files for interactive/non-interactive sessions, which makes avoiding this problem slightly easier.
In case this is helpful, here's my environment: debian 8, gcc (with std = gnu99).
I am facing the following situation:
In my C program, I get a string (char* via a socket).
This string represents a bash command to execute (like 'ls ls').
This command can be any bash, as it may be complex (pipelines, lists, compound commands, coprocesses, shell function definitions ...).
I can not use system or popen to execute this command, so I use currently execve.
My concern is that I have to "filter" certain command.
For example, for the rm command, I can apply it only on the "/home/test/" directory. All other destinations is prohibited.
So I have to prevent the command "rm -r /" but also "ls ls && rm -r /".
So I have to parse the command line that is given me, to find all the command and apply filters on them.
And that's when I'm begin to be really lost.
The command can be of any complexity, so if I want to make pipelines (execve execute a command at a time) or if I want to find all commands for applying my filters, I'll have to develop parser identical to that of sh.
I do not like creating the wheel again, especially if I make it square.
So I wonder if there is a feature in the C library (or that of gnu) for that.
I have heard of wordexp, but I do not see how manage pipelines, redirection or other (in fact, this does not seem made for this) and i do not see how can I retrieve all the command inside the commande.
I read the man of sh(1) to see if I can use it to "parse" but not execute a command, but so far, I find nothing.
Do I need to code a parser from the beginning?
Thank for your reading, and I apologies for my bad english : it's not my motherlanguage (thanks google translate ...).
Your problem:
I am facing the following situation: In my C program, I get a string
(char* via a socket). This string represents a bash command to execute
(like 'ls ls'). This command can be any bash, as it may be complex
(pipelines, lists, compound commands, coprocesses, shell function
definitions ...).
How do you plan on authenticating who is at the other end of the socket connection?
You need to implement a command parser, with security considerations? Apparently to run commands remotely, as implied by "I get a string (char* via a socket)"?
The real solution:
How to set up SSH without passwords
Your aim
You want to use Linux and OpenSSH to automate your tasks. Therefore
you need an automatic login from host A / user a to Host B / user b.
You don't want to enter any passwords, because you want to call ssh
from a within a shell script.
Seriously.
That's how you solve this problem:
I receive on a socket a string that is a shell command and I have to
execute it. But before execute it, i have to ensure that there is not
a command in conflict with all the rules (like 'rm only inside this
directory, etc etc). For executing the command, I can't use system or
popen (I use execve). The rest is up to me.
Given
And that's when I'm begin to be really lost.
Because what you're being asked to do is implement security features and command parsing. Go look at the amount of code in SSH and bash.
Your OS comes with security features. SSH does authentication.
Don't try to reinvent those. You won't do it well - no one can. Look how long it's taken for bash and SSH to get where they are security-wise. (Hint: it's decades because there's literally decades of history and knowledge that were built into bash and SSH when they were first coded...)
I have a shell script which does some functions like making image , downloading tar files,exporting environment variables,download images ...n task etc. I have separate functions for each task. I If I source the shell script it will start running functions one by one. Is there a way to make the functions available to shell without executing it.
Sourcing the shell script will make the function available to shell but it will start executing it.
Actual code:
do_task1();
#some logging here
#shell commands
do_task2();
#error checks
#....
# there are lot of such things as well as user defined functions.
Sourcing this file will actually start executing this since the call to functions exist. I want the user defined functions alone to be available in shell prompt.
One way is to use C style coding ie to have main function which will call other functions. Whenever I want the functions alone to be available in a shell without exec then I could just comment that main call alone. Right now I don't have main function.
function main()
{
do_task1();
#add all the commands and functions here.
do_task2();
}
main # I can comment this.
Is there any other way(or some shell command)to load the functions alone ?
Why I need this ?
It will be useful for debugging .
If I want to run some functions of this shell script I can just run it .
Most shells (like bash and zsh) have support for functions. You can define functions and call them arbitrarily. Sourcing a file with function definitions will not execute them.
I am wanting to make a terminal app that stores information about files/directories. I want a way to keep the information if the file is moved or renamed.
What I thought I could do is have a function execute before any command is run. I found this:
http://www.twistedmatrix.com/users/glyph/preexec.bash.txt
But I was wondering if this would be a good way to go about it. Or should I do something else?
I would like to call that function from a C program whenever mv is entered I suppose.
If what you're trying to do is attach some sort of metadata to files, there's a much better supported way to do that -- extended attributes.
Another solution might be to use the file's inode number as an index into a database you maintain yourself.
Can you alias the mv command? in .profile or .bashrc
alias mv=/usr/bin/local/mymv
where mymv is a compiled executable that runs your C code function and calls /usr/bin/mv.
precmd and preeexec add some overhead to every bash script that gets run, even if the script never calls mv. The downside to alias is that it requires new code in /usr/local and if scripts or users employ /usr/bin/mv instead of mv it will not do what you want. Generally doing something like this often means there is a better way to handle the problem with some kind of service (daemon) or driver. Plus, what happens if your C code cannot correctly handle interesting input like
mv somefille /dev/null
If you want to run command each time after some command was executed in the terminal, just put the following in ~/.bashrc:
PROMPT_COMMAND="your_command;$PROMPT_COMMAND"
If you want your command to be executed each time before mv is executing, put the following in ~/.bashrc:
alias mv="your_script"
Make sure that your script will execute real mv if needed.
You can use inotify library to track filesystem changes. It's good solution, but once user remove file, it's already gone.
You might be able to make use of the DEBUG trap in Bash.
From man bash:
If a sigspec is DEBUG, the command arg is executed before every
simple command, for command, case command, select command, every
arithmetic for command, and before the first command executes in
a shell function
I found this article when I was forced to work in tcsh and wanted to ensure a specific environemtn variable was present when the user ran a program from a certain folder (without setting that variable globally)
tcsh can do this.
tcsh has special alias, one of which is precmd
This can be used to run a script just before the shell prompt is printed.
e.g. I used set precmd 'bash $HOME/.local/bin/on_cd.sh'
This might be one of the very few useful features in csh.
It is a shame but I don't think the same or similar feature is in bash or other sh derivites (ash, dash etc). Related answer.