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A SimpleBluetooth - full code
B nodbus dbus header only
both have dbus as a "wrapper' folder.
I am busy trying to keep the separate but in my own directory stricture.
So I have not actually compare the real headers.
I won't be surprised if the foundation is "bluez
library.
There are too many "clones" of this undocumented source...
seems a waste of talent to keep reinventing " bluez"...
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Hi guys, I'm trying to understand the mechanism behind the Paige-Tarjan algorithm. I searched a lot on the internet but I found only papers with analytical explanations, but I would lite to understand pratically how it works, with an example, an exercise or something else.
I already downloaded the bispy repository on git but I don't understand how it works pratically, which are the steps that lead me to say that this is the result
for an easy example, with this graph:
0 -> 1,2
1 -> 3,4
2 -> 5,6
3,4,5,6 -> null
I can't understand which are the steps that results in:
[(1, 2), (3, 4, 5, 6), (0,)]
I hope someone can explain me this. Thank you all.
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link to the git ?
CI/CD = Continuous Impediment/Continuous Despair
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Extracting the Points from a CRgn Object - C / C++ / MFC ...
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I've an MFC app. When the mouse hovers over a spot, I want a small popup window to appear displaying helpful info. It goes away when the mouse moves etc. How is this done? Need some clues. Thanks.
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It depends on what is in the spot that the mouse is hovering over. Take a look at sme of the following links: mfc tooltip - Google Search[^].
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This is my current resource:
https://www.ibm.com/docs/en/zos/2.1.0?topic=line-using-redirection-symbols
unfortunately I am not sure WHERE the redirection belongs
in my system call parameters.
Here is my TEST code
QFile *resultFile;
system(" echo q | sudo -S hcitool cc --role=c 98:D3:31:F8:29:33 > resultFile");
system(" echo q | sudo -S hcitool info 98:D3:31:F8:39:33 > resultFile");
return;
and the TEST debug result
[sudo] password for nov25-1: Can't create connection: Input/output error
[sudo] password for nov25-1:
neither one provides data output to "resultFile".
Please note that the first "system" call attempts to "connect" and fails ,hence
would not have any data to redirect anyway. Expected with "no
connection " behavior.( Used to test compiler /linker. )
I am asking for help placing the ">resultFile" into system call.
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I don't know what's the difference between the two commands. I don't know what hcitool does, but I don't think that matters.
What the command(s) do, is to pass the string "q" as stdin to sudo . If "q" is the user password, that's fine because sudo expects to read the user password. On my machine I tried:
echo xxxxxx | sudo -S ps -A > results and that works fine. I get the output of ps in the results file ("xxxxxx" is the user "password").
Now how useful or portable such an approach is, is another question.
- Do you plan to have user's password embedded in your code? What if you change your password? would you recompile the code or what?
- Wouldn't it be simpler to just accept that your code has to be run as root?
- Maybe you can set hcitool to be run with sudo without a password. Take a look at Sudoers Manual[^]:
Quote: PASSWD and NOPASSWD
By default, sudo requires that a user authenticate before running a command. This behavior can be modified via the NOPASSWD tag. Like a Runas_Spec, the NOPASSWD tag sets a default for the commands that follow it in the Cmnd_Spec_List. Conversely, the PASSWD tag can be used to reverse things. For example:
ray rushmore = NOPASSWD: /bin/kill, /bin/ls, /usr/bin/lprm
would allow the user ray to run /bin/kill, /bin/ls, and /usr/bin/lprm as root on the machine “rushmore” without authenticating himself. If we only want ray to be able to run /bin/kill without a password the entry would be:
ray rushmore = NOPASSWD: /bin/kill, PASSWD: /bin/ls, /usr/bin/lprm
Mircea
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Here is my test code :
system( "echo q | sudo -S ps -A "); return;
and partial output to console
sudo] password for nov25-1: PID TTY TIME CMD
1 ? 00:00:07 systemd
2 ? 00:00:00 kthreadd
3 ? 00:00:00 rcu_gp
4 ? 00:00:00 rcu_par_gp
5 ? 00:00:00 slub_flushwq
6 ? 00:00:00 netns
8 ? 00:00:00 kworker/0:0H-events_highpri
11 ? 00:00:00 mm_percpu_wq
12 ? 00:00:00 rcu_tasks_kthread
13 ? 00:00:00 rcu_tasks_rude_kthread
no output with "resultFile"
hence
same outcome as with original code
PS
ONLY , so far , the "hcitool info" require password AND current system call passing it works as expected.
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This works for me:
#include <stdlib.h>
#include <stdio.h>
int main ()
{
int ret;
ret = system ("echo xxxxxx | sudo -S ps -A >results");
printf ("ret=%d\n", ret);
return 0;
} The output goes to "results" file and ret is 0.
Environment: Ubuntu 22.04LTS freshly installed yesterday.
Compiler: gcc 11.1.0
Mircea
modified 19-Feb-24 21:48pm.
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Just to make sure - how is your results file declared /defined?
I am getting correct return value but no data anywhere - no console or file.
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It doesn’t exist before running the program. It is created by the command. If you want to read it, you should open it after the command has finished.
Mircea
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Kindly allow me to "write review".
The OP question was answered.
by placing the redirection as last option of the system call.
Ir was verified by passing by complier / linker and function
returning success ( 0 ).
However, as coded there is no "passed to " function seen in debugger,
( since it is part of the options ?)
and
there is no practical value of the "passed to " function if it cannot be read.
hence there is an extension to my OP
how to read the contents of the "passed to" function ?
after that question extension is answered there will be another
modification
how to "pipe" ca;; result to the console and redirect it to a file SAME time ?
I sincerely appreciate your contribution to resolve this.
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I'm not sure I understand your question. Something might be "lost in translation".
You cannot send results to file and console "at the same time". What you can do is send them to the console right after you sent them to the file. For instance:
ps -A >results && cat results
If what you want is to read the results in your program and process them somehow, you could do something like:
#include <stdlib.h>
#include <stdio.h>
int main ()
{
int ret;
char line[256];
ret = system ("echo xxxxxx | sudo -S ps -A >results");
FILE *f = fopen("results", "r");
while (!feof(f)) {
fgets (line, sizeof(line), f);
puts(line);
}
fclose(f);
return 0;
} I didn't compile this code but should be rather OK.
If you explain better what you want to do maybe I can answer more to the point.
Mircea
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Mircea Neacsu wrote: You cannot send results to file and console "at the same time"
At the risk of further confusing the OP, I'd like to remind you of the tee command
$ ls | tee /tmp/foo
PID TTY TIME CMD
3995778 pts/1 00:00:00 bash
3995865 pts/1 00:00:00 ps
3995866 pts/1 00:00:00 tee
$ cat /tmp/foo
PID TTY TIME CMD
3995778 pts/1 00:00:00 bash
3995865 pts/1 00:00:00 ps
3995866 pts/1 00:00:00 tee
But to the OP's issue, I'd like to, once again, point out that system() is not an ideal tool to use if you want to capture command output. A better option would be to use popen() or a QProcess object. The masochists could also write their own process object that allows reading and writing to the child process, but that's an adventure not for the faint of heart.
"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown
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k5054 wrote: I'd like to remind you of the tee command
True! I forgot about good old tee Too much time spent in Windowsland
Mircea
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I believe it is time to say that the problem has been solved.
I now have enough info to figure out why
hcitool info 98:D3:31:F8:39:33 takes almost 20 seconds to "complete", however , it goes from immediate " connect " to "disconnect" in few seconds...
(hcitool problem outside CodeProject scope )
In retrospect I would like to point out that I am still not sure how
echo q | sudo -S hcitool cc --role=c 98:D3:31:F8:29:33
works
how do I get "user" in console , but not "password"?
There was two reasons why I shy away from QProcess
I am being chastised every time I ask Qt question, but it is OK to keep showing QProcess to me
especialy when I do not know what is "program" in
echo q | sudo -S hcitool cc --role=c 98:D3:31:F8:29:33
command.
(obviously Qt question )
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Salvatore Terress wrote: obviously Qt question No, nothing to do with Qt. But then that is (the main) part of your problem, you seem to be confused between what is Qt, the language library or the Linux shell.
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UPDATE ( just to share )
here is working as expected C++ code
system(" echo q | sudo -S hcitool cc --role=c 98:D3:31:F8:29:33");
and here is the result:
[sudo] password for nov25-1: Can't create connection: Input/output error
what is interesting "echo" hides the passed password
the challenge - how to hide [sudo] password for nov25-1:
modified 17-Feb-24 12:05pm.
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Googling provides answers
C++ "sudo" provide password
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Try using a Here Document :
[k5054@localhost]$ sudo ps
[sudo] password for k5054:
sudo: no password was provided
sudo: a password is required
[k5054@localhost]$ cat example.cpp
int main()
{
std::string userPass{"myPassword"};
std::string command{"sudo -S ps -lf 2>/dev/null <<_EOF\n" + userPass + "\n_EOF"};
FILE *pipe = popen(command.c_str(), "r");
char *line = NULL;
size_t len = 0;
ssize_t rlen;
while( (rlen = getline(&line, &len, pipe)) > 0) {
line[--rlen] = '\0'; // trim trailing newline
std::cout << line << '\n';
}
pclose(pipe);
free(line);
}
[k5054@localhost]$ make example
g++ -Wall -Wextra -ggdb example.cpp -o example
[k5054@localhost]$ ./example
F S UID PID PPID C PRI NI ADDR SZ WCHAN STIME TTY TIME CMD
1 S root 4030 4029 0 80 0 - 4799 do_pol 11:49 pts/2 00:00:00 sudo -S ps -lf
4 R root 4031 4030 0 80 0 - 3502 - 11:49 pts/2 00:00:00 ps -lf
[k5054@localhost]$ You should be able to modify that for use with QProcess.
Note that if you don't redirect stderr to /dev/null, the SSH password prompt goes to wherever stderr is pointing to.
"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown
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