Spawn a child process, given a list of arguments
#include <process.h> int spawnl( int mode, const char * path, const char * arg0, const char * arg1..., const char * argn, NULL );
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The spawnl() function creates and executes a new child process, named in path with a NULL-terminated list of arguments in arg0 … argn. This function calls spawnve().
|If the new child process is a shell script, the first line must start with #!, followed by the path of the program to run to interpret the script, optionally followed by one argument. The script must also be marked as executable. For more information, see “The first line” in the Writing Shell Scripts chapter of the Neutrino User's Guide.|
The spawnl() function isn't a POSIX 1003.1 function, and isn't guaranteed to behave the same on all operating systems. It builds an argv[ ] array before calling spawn().
To view the documentation for a function, click its name in this diagram:
Arguments are passed to the child process by supplying one or more pointers to character strings as arguments. These character strings are concatenated with spaces inserted to separate the arguments to form one argument string for the child process.
The child process inherits the parent's environment. The environment is the collection of environment variables whose values that have been defined with the export shell command, the env utility, or by the successful execution of the putenv() or setenv() function. A program may read these values with the getenv() function.
|A parent/child relationship doesn't imply that the child process dies when the parent process dies.|
The spawnl() function's return value depends on the mode argument:
|P_WAIT||The exit status of the child process. For information about macros that extract information from this status, see “Status macros” in the documentation for wait().|
|P_NOWAIT||The process ID of the child process. To get the exit status for a P_NOWAIT process, you must use the waitpid() function, giving it this process ID.|
|P_NOWAITO||The process ID of the child process, or 0 if the process is being started on a remote node. You can't get the exit status of a P_NOWAITO process.|
If an error occurs, -1 is returned (errno is set).
See also the errors for ConnectAttach() and MsgSendvnc().
Run myprog as if the user had typed:
myprog ARG1 ARG2
on the command line:
#include <stddef.h> #include <process.h> int exit_val; … exit_val = spawnl( P_WAIT, "myprog", "myprog", "ARG1", "ARG2", NULL ); …
The program is found if myprog is in the current working directory.
|Cancellation point||Read the Caveats|
If mode is P_WAIT, this function is a cancellation point.
execl(), execle(), execlp(), execlpe(), execv(), execve(), execvp(), execvpe(), getenv(), putenv(), setenv(), spawn(), spawnle(), spawnlp(), spawnlpe(), spawnp(), spawnv(), spawnve(), spawnvp(), spawnvpe(), wait(), waitpid()
Processes and Threads chapter of Getting Started with QNX Neutrino