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Hide sh: -c error messages when calling “system” in c++ Linux


Hide sh: -c error messages when calling “system” in c++ Linux

By : user2954056
Date : November 21 2020, 07:31 AM
wish help you to fix your issue Think that system forks a process and then executes the command you've provided. The new process inherits the descriptor from its parent and that new process is writing in its standard error.
So, this code snippet may do what you want:
code :
#include <stdlib.h>
#include <unistd.h>

int main()
{
    int duperr;
    duperr = dup(2);
    close(2); /* close stderr so the new process can't output the error */
    system("date '");
    dup2(duperr, 2);
    close(duperr);
    /* here you can use stderr again */
    write(2, "hello world\n", 12);
    return 0;
}
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>

int main(void) {
    int devnull_fd, duperr_fd;
    /* get a descriptor to /dev/null (devnull_fd) */
    devnull_fd = open("/dev/null", O_WRONLY | O_APPEND);
    /* save a descriptor "pointing" to the actual stderr (duperr_fd) */
    duperr_fd = dup(STDERR_FILENO);
    /* now STDERR_FILENO "points" to "/dev/null" */
    dup2(devnull_fd, STDERR_FILENO); 

    system("date '");
    /* restore stderr */
    dup2(duperr_fd, STDERR_FILENO);
    close(duperr_fd);
    close(devnull_fd);
    /* here you can use stderr again */
    write(STDERR_FILENO, "hello world\n", 12);
    return 0;
}


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How to replace Linux Kernel error messages with my defined error messages?

How to replace Linux Kernel error messages with my defined error messages?


By : hamburgler
Date : March 29 2020, 07:55 AM
wish help you to fix your issue I have created a shell and when I give wrong number of arguments like insufficient arguments to cp commands I receive the Linux shell error message like what you will receive if you type cp fork.c as follows:
code :
cp fork.c > /dev/null 2>&1 || echo "Dude! this is an error"
Linux System Call: Custom Control Messages

Linux System Call: Custom Control Messages


By : user6839484
Date : March 29 2020, 07:55 AM
fixed the issue. Will look into that further Have a look at the ioctl system call - http://man7.org/linux/man-pages/man2/ioctl.2.html
If you were writing your own device driver you'd use ioctl to send device-specific control instructions.
Error when calling request binary, system exit code: 126, text output, Error when calling response binary, system exit c

Error when calling request binary, system exit code: 126, text output, Error when calling response binary, system exit c


By : Andy
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , To resolve this issue you have to make sure, that those files are actually binaries. If you've transferred them i.e. by filezilla ftp client then transfer is not in binary mode by default.
Unpack them directly from archive on server or change transfer settings should resolve that issue.
Is there any way to retrieve the severity level of the messages from system log in linux?

Is there any way to retrieve the severity level of the messages from system log in linux?


By : Tarishi Saxena
Date : March 29 2020, 07:55 AM
Hope this helps I'm not as familiar with the older format (and I've not tested this), but this may do what you're looking for:
code :
## ------------------------------------------------------ #
## All levels in a seperate file
*.emerg                         -/var/log/log.0_emergency
& stop

*.alert;*.!emerg                -/var/log/log.1_alert
& stop

*.crit;*.!alert                 -/var/log/log.2_critical
& stop

*.err;*.!crit                   -/var/log/log.3_error
& stop

*.warning;*.!err                -/var/log/log.4_warning
& stop

*.notice;*.!warning             -/var/log/log.5_notice
& stop

*.info;*.!notice                -/var/log/log.6_info
& stop

*.debug;*.!info                 -/var/log/log.7_debug
& stop
if ($syslogfacility-text == 'auth') 
    or ($syslogfacility-text == 'authpriv') then {

    action(
        name="auth-log"
        type="omfile"
        file="/var/log/auth.log")

    stop
}

# Keep cron messages in their own dedicated file
if ($syslogfacility-text == 'cron') then {
    action(
        name="cron-log"
        type="omfile"
        file="/var/log/cron.log")

    stop
}
Capturing error messages when calling Matlab from Linux bash

Capturing error messages when calling Matlab from Linux bash


By : Farhan Nazir
Date : September 27 2020, 05:00 AM
will help you You are catching the error, without doing anything with the encountered error. Instead, catch the exception and display it. In a script/function this would look like:
code :
try
    someNonExistingFunction()
catch ME
    disp(ME)
end
ME = 
  MException with properties:

    identifier: 'MATLAB:UndefinedFunction'
       message: 'Undefined function or variable 'someNonExistingFunction'.'
         cause: {}
         stack: [0×1 struct]
    Correction: []
matlab -nodisplay -r "try; someFunction(); catch ME; disp(ME); end; quit"
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