Updated: April 19, 2023

Execute a system command


#include <stdlib.h>

int system( const char *command );


NULL, or the system command that you want to execute; see below.



Use the -l c option to qcc to link against this library. This library is usually included automatically.


The behavior of the system() function depends on the value of its command argument:

Note: The shell used is always sh, regardless of the setting of the SHELL environment variable, because applications may rely on features of the standard shell, and may fail as a result of running a different shell.

This means that any command that can be entered to the OS can be executed, including programs, QNX Neutrino commands, and shell scripts. The exec*() and spawn*() functions can only cause programs to be executed.


For information about macros that extract information from the value returned by system(), see Status macros in the description of wait().

When an error has occurred, errno contains a value that indicates the type of error that has been detected. In particular, see the error codes for spawn().


#include <stdlib.h>
#include <stdio.h>
#include <sys/wait.h>

int main( void )
    int rc;

    rc = system( "ls" );
    if( rc == -1 ) {
      printf( "shell could not be run\n" );
    } else {
      printf( "result of running command is %d\n",
          WEXITSTATUS( rc ) );
    return EXIT_SUCCESS;


ANSI, POSIX 1003.1

Cancellation point Yes
Interrupt handler No
Signal handler No
Thread Yes