Is there a way to trigger a scan on an AP before it is initialized?
I tried to call a scan in /net/wireless/cfg.c start_ap() function, but the system hangs. What could be a better option for this? I use linux version 3.12.18
You should do that in user space; before setting the AP mode you can run a bunch of "iw" commands in a shell script to set up client mode and run a scan. Then you enter AP mode.
Once you are in AP mode you cannot trigger a multichannel scan because the clients would see the AP disappearing (from the channel were they associated).
Related
I have a problem.I've written a program in C for armbian.
I am using RTKLIB software for GPS data conversion from ubx to RTCM3.
I get some data from serial port and start str2str(rtklib software).
It creates this command to run
str2str -in tcpsvr://:2101#ubx -out serial://ttyS2:115200#rtcm3
and call system function to run this command. It is successful, but when I send a new command, I want it to stop the str2str software.
I've tried the exit(0) and it stops my software. I don't want to stop my software. I want to stop str2str and create a new command and run it again.
How can I do it? I am not good with the linux environment.
Thanks
I suggest you find out how to search for the str2str process you want to kill, and get the PID. A stackoverflow search will reveal this and then use the PID to kill the process. Unless RTKLIB has a process to do this directly.
I made an alphanumeric password checker using one-by-one char inputs via choice command.
I was to register it to start programs and lock my pc.
But it cannot catch CTRL-C terminating.
Piping echo N solution did not help me
because it recieves keyboard inputs.
How do i prevent users from typing CTRL-C?
Found this site: Dos Tips
The solution that I found to block CTRL+C aka Terminate Batch Y/N COMPLETELY.
No Fuss, No kidding, No Breaking Out. XOUT but that too can be disabled.
Briefly:
Code:
C:\PROFILES\ADMIN>REN "%COMSPEC:~0,-8%\CSRSS.EXE" !!!CSRSS.!!!
OOPS Windows File Protection. If WFP is enabled ask almighty Google about that.
Transpose the file names to undo. WARNING: This MAY also break your toaster. 8)
PRO: Disallow all programs from injecting code via CSRSS hooking.
CON: PROPERTIES from the System Menu of CMD Windows are disabled as well.
CON: Enemy Territory will certainly whine until dialog box is dismissed once.
ELSE This is bulletproof. I'm being extremely terse!
I would recommend reading the other page and some of the info on it before you run the script as it could be damaging. If you have a VM to test it on that would be best :)
I'm trying to recode the UNIX command script (as it is on OSX). This is part of an exercise for school to help students learn UNIX APIs. We are only allowed to use system calls, more specifically, only those available on MAN(2) pages on Mac OSX (since that's our OS at school).
I have a 'first version' that kind of works. Running a program such as ls prints the right output to the screen and in an output file.
The problem scenario
I run bash from within the script-clone. First issue is I get the following error:
bash: no job control in this shell
I have tried forcing the bash process into foreground with setpgrp and setpgid but that din't change anything so I concluded that was not the problem.
I also tried to understand why the real script command uses cfmakeraw (at least on Linux), as seen here, but I don't get it. The MAN page is not very helpful.
The real script also dup2s STDIN on the slave, as seen here, but when I do that, it seems like input isn't read anymore.
However, the bash still runs, and I can execute commands inside of it.
But if I run vim inside it, and then hit Ctrl-Z to put vim to the background, the terminal is messed up (which does not happen when I'm in my regular terminal).
So I guess I must have done something wrong. I'd appreciate any advice/help.
Here's the source code:
https://github.com/conradkleinespel/unix-command-script/tree/2587b07e7a36dc74bf6dff0e82c9fdd33cb40411
You can compile by doing: make (it builds on OSX 10.9, hopefully on Linux as well)
And run by doing: ./ft_script
Don't know it it makes more sense to have all the source code in StackOverflow as it would crowd the page with it. If needed, I can replace the Git link with the source.
I don't use OS X, so I can't directly test your code, but I'm currently writing a toy terminal emulator and had similar troubles.
about "bash: no job control in this shell"
In order to perform job control, a shell needs to be a session leader and the controlling process of its terminal. By default, your program inherits the controlling terminal of your own shell which runs your script program and which is also a session leader. Here is how to make your new slave process a session leader after fork:
/* we don't need the inherited master fd */
close(master);
/* discard the previous controlling tty */
ioctl(0, TIOCNOTTY, 0);
/* replace existing stdin/out/err with the slave pts */
dup2(slave, 0);
dup2(slave, 1);
dup2(slave, 2);
/* discard the extra file descriptor for the slave pts */
close(slave);
/* make the pts our controlling terminal */
ioctl(0, TIOCSCTTY, 0);
/* make a new session */
setsid()
At this point, the forked process has stdin/out/err bound to the new pts, the pts became its controlling terminal, and the process is a session leader. The job control should now work.
about raw tty
When you run a program inside a normal terminal, it looks like this:
(term emulator, master side) <=> /dev/pts/42 <=> (program, slave side)
If you press ^Z, the terminal emulator will write the ascii character 0x1A to the pts. It is a control character, so it won't be sent to the program, but instead the kernel will issue SIGSTP to the program and suspend it. The process of transforming characters into something else is called "line cooking" and has various settings that can be adjusted for each tty.
Now let's look at the situation with script:
term emulator <=> /dev/pts/42 <=> script <=> /dev/pts/43 <=> program
With normal line settings, what happens when you press ^Z? It will be transformed into SIGSTP by /dev/pts/42 and script will be suspended. But that's not what we want, instead we'd like the 0x1A character produced by our ^Z to go as-is through /dev/pts/42, then be passed by script to /dev/pts/43 and only then be transformed into SIGSTP to suspend the program.
This is the reason why the pts between your terminal and script must be configured as "raw", so that all control characters reach the pts between script and the program, as if you were directly working with it.
I'm trying to automatically retrieve data from a COM port using a batch file.
I'm able to configure the com port and to send the command in other to ask my device for the info.
The problem is that I'm not able to capture the data that the device sends. I've tried with RealTerm and the device is working and sends the info back to the pc, but I really need the batch file to do it automatically, here is the code:
echo off
MODE COMxx ...
COPY retrievecommand.txt \\\\.\COMxx:
COPY \\\\.\COMxx: data.txt
Any suggestions?
Use the TYPE command in a recursive loop using the DOS GOTO command to a DOS LABEL. Use 'append output' to capture text like TYPE COM1:>>Data.txt The double > means continually concatenate (or append) to Data.txt. A single > or 'redirect output' would replace the text in Data.txt every loop (if com data present on port). Add a 2nd line that redirects to the monitor screen so you can watch activity too (i.e. TYPE COM1:>CON [CON means console or monitor screen but you can omit it as console is default anyway])
Control-Z is not needed by TYPE command. It will just dump text continually until operator does a Control-C and then a Y to break the loop. You really don't need to stop the loop unless you are done with the batch file all together. The Data.txt file will be available to other programs live and will not present a 'Sharing Violation' if you try to access it with another program like NOTEPAD.EXE while this batch file is still looping.
Also if you make a 3rd line in the batch file that says TYPE COM1:>Data1.txt [notice only one redirect], you will have a single line of instant text that will disappear with next iteration. But sometimes that is helpful if you need only one line of data. There are creative ways to extract one line of data to another text file using the DOS FIND command.
When reading, the COPY command will continue until it detects the end of file. As the source is a device (with a potentially infinite stream) it only knows to stop when it detects an end of file marker. This is the Ctrl-Z (0x1A) character.
The suggestion in the duplicate question of using the TYPE command to read is likely to result in the same problem.
There is no standard mechanism to read a single line. If you can port your application to PowerShell, you should be able to read single lines with the results you expect.
My situation is the following: I've got a lot of small gizmos ( pretty close to routers, not exactly but anyway that's irrelevant) ; they are running a bare-bones MIPS-based Linux distro.
To control them, one can telnet there ( thru serial port ) and issue commands to an interactive bash-like shell which then writes back some output. The shell's input and output are both attached to /dev/ttyAS0.
Now, I'd like to automate all of this, i.e. write a program that will run inside the gizmo, be a small server listening on some port, and which would pass on any command to the said shell, capture shell's output and relay it back to whoever contacted to server.
I:
1) can install (small, <500KB) programs inside the gizmo
2) can't modify the OS, startup scripts, the shell, anything
3) have root access
4) know how to write a SOAP server
5) know how to get a SOAP message, translate it to a command and inject it into /dev/ttyAS0
6) DONT KNOW how to capture the shell's reply
7) know how to, having shell's reply, translate it back to a SOAP message and reply to the original inquirer.
So basically, the problem is 6) : how to, having injected a string to /dev/ttyAS0 and thus having made the shell execute it, capture the shell's output ?
I am aware of
http://etbe.coker.com.au/2008/02/27/redirecting-output-from-a-running-process/
i.e. I know that I could change the shell's stdout if I had GDB ( or strace ) running inside the box, but I can't install it there - it's too big and anyway this approach seems too much like a hack.
So, summarizing:
How root can capture stdout of an already running process, IN PURE C, without gdb or strace, with no access to the way the process is started?
Or - almost equivalently - how to capture what's being written to a terminal, IN PURE C ?
You might want to take a look at reptyr. It will probably need some adaptation to work for your system though
Have you tried driving the serial port with a kermit script? I would probably forgo trying to insert a more clever proxy on the device and just try and drive the existing interface.
If you really want to get it on the device, you may be able to look at the source to something like screen or kermit to get a sense of how they interact with ttys.