I have a script where I launch a shell command. The problem is that the script doesn't wait until the command is finished and continues right away.
I have tried WAIT but it doesn't work as the shell command turns the source off and on (ignition off/on) and I get the error that WAIT cannot be executed because power is off.
Is there any command I can use for program to wait until the command is executed?
My script looks like this:
OS.COMMAND echo OUTP OFF > COM1
OS.COMMAND echo OUTP ON > COM1
System.up
If I would want to execute a shell command without redirecting I would use OS.Area instead of OS.Command, because OS.Area is blocking and will wait until the shell command has finished. However OS.Area does not support redirecting I think.
If I would want to execute a shell command and redirect the output to a file I would first delete the file and then wait until it gets accessible. Like this:
IF OS.FILE.EXIST("myfile.txt")
RM "myfile.txt"
OS.Command ECHO "Hello World" > "myfile.txt"
WAIT OS.FILE.readable("myfile.txt")
However it looks like you want to write via a shell command to a COM port on Windows. But I don't think it is possible to wait in TRACE32 until this write to the COM port has been done when using OS.Command...
So I suggest to do this task with the TERM commands instead:
TERM.METHOD #1 COM COM1 115200. 8 NONE 1STOP NONE
TERM.view #1
TERM.Out #1 "OUTP OFF" 0x0A
TERM.Out #1 "OUTP ON" 0x0A
Of course you have to set the correct baud rate, bits, parity and stop bits. The 0x0A after each TERM.Out is simply the line-feed character.
Does you terminal show any output as a reaction to OUTP ON? If yes you can also wait for this output with e.g. SCREEN.WAIT TERM.LINE(#1,-1)=="OUTP is now ON" 5.s
Otherwise I assume that a simple WAIT 50.ms before SYStem.Up will probably do the trick too.
Related
I have a C++ program which is called at startup via a cronjob (in crontab):
#reboot sudo /home/pi/CAN/RCR_datalogging/logfileControl
Which does run logfileControl anytime the Pi is booted as it shows up in the list of running programs (ps -e). LogfileControl contains two system calls to C++ programs related to SocketCAN (SocketCAN is part of the Linux Kernel, it allows for dealing with CAN data as network sockets). I want logfileControl to run on startup so that it can initialize the CAN socket (system call 1) and then start the first logfile (systemcall 2, candumpExternal, this is candump from socketCAN with a minor modification to make the logfile a specific location rather than just where candump is, but using the original version had the same issue). The first systemcall seems to be working properly as if I try and initialize the socket again it is busy, but the second systemcall doesn't appear to be happening as a logfile is not created at all as a logfile is not created. If I manually run logfileControl from the command line it works as expected and creates the logfile which has left me quite confused...
Does anyone have an insight as to what is going on here?
system("sudo /sbin/ip link set can0 up type can bitrate 500000");
// This is ran initially as logging should start as soon as the pi is on
system("/home/pi/CAN/RCR_datalogging/candumpExternal can0 -l -s 0"); // candump with the option to log(-l) as well as
// continue to output to console (-s 0)
std::cout <<"Setup Complete" << std:: endl;
while(true) { //sleeping indefinitely so that the program can stay open and wait for button presses
sleep(60);
}
Edit: I also tried adding a simple 5 second pause at the beginning of the program, but this didn't seem to make any difference.
I'm doing make all -d --trace
How do I get Gnu Make to output timestamps for every line it outputs?
More generally, how do I add a timestamp to every STDOUT and STDERR statement?
There is a solution for Linux/Bash but I'm on Windows.
I created a one line batch file add_ts.bat : echo %time% %1
I tried the following but I only got one timestamp (without the lines that were output):
make all --trace -d 2>&1 | add_ts.bat
To a first approximation you need a batch file like:
add_ts.bat
#for /F "usebackq delims==" %%i in (`%1`) do #echo %time% %%i
which you would run like:
add_ts.bat "make all -d --trace" > buildlog.txt
This however isn't good enough if you want to capture and
timestamp STDERR as well as STDOUT from the command passed as
%1, because the backticks operator around %1 will only capture STDOUT
To fix this you'll need to capture STDERR as well as STDOUT within the backticks, by using redirection in there, which in turns means
you need to run a subshell to understand the redirection, and you need to
escape the redirection operators so they're not interpreted by the toplevel
shell. Which all comes to:
#for /F "usebackq delims==" %%i in (`cmd /C %1 2^>^&1`) do #echo %time% %%i
Run just the same way.
Later
what I don't get is why the | itself wasn't enough to send STDOUT and STDERR to STDIN of add_ts.bat
It is. I think you are labouring under the combination of two misconceptions.
One: You believe that a program's commandline arguments are the same as its standard
input, or that it gets it commandline arguments from its standard input. It doesn't.
A program's commandline arguments, if any, are passed to it as a fixed list
of strings in the program-startup protocol. Its standard input is an input stream made
available to it at the same time by the OS and connected by default to the console in which the program
starts. This default can be overridden in the shell by redirection operators. The contents of that input stream are not fixed in advance. It will feed to the
the program whatever is input to the console, or from its redirected proxy, as long as the program is running, as and when the program reads it. The program
can parse or ignore its commandline arguments and, quite independently of that, it can read or ignore its standard input.
Your program add_ts.bat is a program that parses the first of its commandline arguments
- it uses %1 - and ignores any more. And it ignores its standard input entirely.
Two: You believe that the effect of a pipeline, e.g.
a | b
is to start an a process and then, for each line that it writes to the standard output, start
a distinct b process which will automatically receive that one line written by a as
a single commandline argument (no matter who many words are in the line) and do its stuff
with that single commandline argument.
That's not what happens. The OS starts one a process and one b process, and connects the
standard output of the one a process to the standard input of the one b process. For the
pipeline to work at all, b has got to be a program that reads its standard input. Your
add_ts.bat is not such a program. It's only a program that parses its first commandline
argument: the | doesn't give it any, and the commandline:
make all --trace -d 2>&1 | add_ts.bat
doesn't give it any either. The commandline:
make all --trace -d 2>&1 | add_ts.bat "Hello World"
would give it one commandline argument and:
make all --trace -d 2>&1 | add_ts.bat Hello World
would give it two, not one, commandline arguments, the second being ignored. But in any case
it doesn't read its standard input so piping to it is futile.
The site ss64.com is perfectly good about CMD redirection and piping
but it assumes you know what a program has to do to be a pipeline-able command: To be an upstream command,
it has to write its standard output; to be a downstream command it has to read its standard input.
Using a batch file wrapper is a clever solution if you don't mind the extra overhead. Otherwise I think you'll have to modify GNU make itself to have it print out this data.
If that's not palatable for some reason, you can get that information by using ElectricMake, a GNU-make-compatible implementation of make that includes lots of enhancements, including annotated build logs that have microsecond-resolution timestamps for every job in the build. ElectricMake is part of ElectricAccelerator Huddle.
Here's a bit of the annotation for a trivial "echo Hello World!" job:
<job id="J00007fb820002000" thread="7fb82f7fe700" start="3" end="4" type="rule" name="all" file="
Makefile" line="1">
<command line="2">
<argv>echo Hello, world!</argv>
<output src="prog">Hello, world!
</output>
</command>
<commitTimes start="0.291693" wait="0.296587" commit="0.296628" write="0.296680"/>
<timing invoked="0.291403" completed="0.296544" node="ecdroid3a-59"/>
</job>
Here, the <timing> tag shows the start time (0.291403 seconds) and end time (0.296544 seconds) of the job relative to the start of the build.
These annotated build logs can be viewed and analysed graphically with ElectricInsight, a companion tool for ElectricMake.
ElectricAccelerator Huddle is the freemium version of ElectricAccelerator -- usage is entirely free up to a point, with modest pay-as-you-go fees beyond that
Disclaimer: I'm the architect of ElectricAccelerator.
Question: Using C++ or a bash/shell script, how can I evaluate output of a long running linux process?
Example:
root#example.com~# iw event
(This command will run until manually killed.)
(It will output data that I will want to read and parse line by line.)
What is the most efficient way to evaluate the std output of this command when a new line is added to its buffer?
For example: iw event will output a line that says:
new station: 0e:0e:20:2d:20
I want to detect "new station" and run another command with the mac address. IE:
./myProgram -mac 0e:0e:20:2d:20
Thanks!
If you run the command as shown, all output will go to stdout and display on the terminal. To capture the output you have a few options:
Pipe the output to your monitor program, as in iw events | yourmonitorprogram which then reads stdin. iw should probably be modified to use unbuffered output.
Write the output of iw to a file and then use the same technique as the tail -f command to poll the file periodically
Have iw write to a named pipe or socket and have your monitor program read from that pipe or socket. This option requires modification to iw.
The simplest option is the first one
i have an interface where i use to execute the mml command in my solaris unix like below:
> eaw 0004
<RLTYP;
BSC SYSTEM TYPE DATA
GSYSTYPE
GSM1800
END
<
As soon as i do eaw <name> on the command line.It will start an interface where in i can execute mml commands and i can see the output of those commands executed.
My idea here is to parse the command output in c++.
I can do away with some logic for parsing.But to start with How can get the command to be executed inside c++ ? Is there any predefined way to do this.
This should be similar to executing sql queries inside c++.But we use other libraries to execute sql queries.I also donot want to run a shell script or create temporary files in between.
what i want is to execute the command inside c++ and get the output and even that in c++.
could anybody give me the right directions?
You have several options. From easiest and simplest to hardest and most complex to use:
Use the system() call to spawn a shell to run a command
Use the popen() call to spawn a subprocess and either write to its standard input stream or read from its standard output stream (but not both)
Use a combination of pipe(), fork(), dup()/dup2(), and exec*() to spawn a child process and set up pipes for a child process's standard input and output.
The below code is done with the sh command. This redirects stdout to a file named "out" which can be read later to process the output. Each command to the process can be written through the pipe.
#include <stdio.h>
int main()
{
FILE *fp;
fp = popen("sh > out", "w");
if (fp) {
fprintf(fp, "date\n");
fprintf(fp, "exit\n");
fclose(fp);
}
return 0;
}
I've got a GUI C++ program that takes a shell command from the user, calls forkpty() and execvp() to execute that command in a child process, while the parent (GUI) process reads the child process's stdout/stderr output and displays it in the GUI.
This all works nicely (under Linux and MacOS/X). For example, if the user enters "ls -l /foo", the GUI will display the contents of the /foo folder.
However, bash niceties like output redirection aren't handled. For example, if the user enters "echo bar > /foo/bar.txt", the child process will output the text "bar > /foo/bar.txt", instead of writing the text "bar" to the file "/foo/bar.txt".
Presumably this is because execvp() is running the executable command "echo" directly, instead of running /bin/bash and handing it the user's command to massage/preprocess.
My question is, what is the correct child process invocation to use, in order to make the system behave exactly as if the user had typed in his string at the bash prompt? I tried wrapping the user's command with a /bin/bash invocation, like this: /bin/bash -c the_string_the_user_entered, but that didn't seem to work. Any hints?
ps Just calling system() isn't a good option, since it would cause my GUI to block until the child process exits, and some child processes may not exit for a long time (if ever!)
If you want the shell to do the I/O redirection, you need to invoke the shell so it does the I/O redirection.
char *args[4];
args[0] = "bash";
args[1] = "-c";
args[2] = ...string containing command line with I/O redirection...;
args[4] = 0;
execv("/bin/bash", args);
Note the change from execvp() to execv(); you know where the shell is - at least, I gave it an absolute path - so the path-search is not relevant any more.