Spawn a child process, given a list of arguments, an environment, and a relative path
int spawnlpe( int mode,
const char * file,
const char * arg0,
const char * arg1...,
const char * argn,
const char * envp );
- How you want to load the child process, and how you want the parent
program to behave after the child program is initiated:
- P_WAIT — load the child program into available
memory, execute it, and make the parent program resume execution after
the child process ends.
- P_NOWAIT — execute the parent program
concurrently with the new child process.
- P_NOWAITO — execute the parent program
concurrently with the new child process.
You can't use
to obtain the exit code.
- P_OVERLAY — replace the parent program with
the child program in memory and execute the child.
No return is made to the parent program.
This is equivalent to calling the appropriate exec*()
- The name of the executable file.
If this argument contains a slash, it's used as the pathname of the
executable; otherwise, the function searches for file in the
directories listed in the PATH environment variable.
- arg0, ... argn, NULL
- The arguments that you want to pass to the new process.
You must pass at least arg0, which by convention is a pointer
to the name of the new child process, and can't be NULL.
You must terminate the list with an argument of NULL.
- NULL, or a pointer to an array of character pointers,
each pointing to a string that defines an environment variable.
The array is terminated with a NULL pointer.
Each pointer points to a character string of the form:
that's used to define an environment variable.
Use the -l c option to
to link against this library.
This library is usually included automatically.
The spawnlpe() function creates and executes a new child process,
named in file with NULL-terminated list of arguments in
arg0 … argn
and with the environment specified in envp. This function calls
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 spawnlpe() function isn't a POSIX 1003.1 function,
and isn't guaranteed to behave the same on all operating systems.
It builds argv[ ] and envp[ ] arrays before calling spawnp().
To view the documentation for a function, click its name in this diagram:
Most of the spawn*() functions do a lot of work before a message is sent to
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.
If the value of envp is NULL, then the child process
inherits the environment of the parent process.
The new process can access its environment by using the
global variable (found in <unistd.h>).
||A parent/child relationship doesn't imply that the child process dies when the parent process dies.|
The spawnlpe() function's return value depends on the mode argument:
||The exit status of the child process.
||The process ID of the child process.
To get the exit status for a P_NOWAIT process, you must use the
giving it this process ID.
||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).
- The number of bytes used by the argument list or environment list of the new child process
is greater than ARG_MAX bytes.
- Search permission is denied for a directory listed in the path prefix
of the new child process or the new child process's file doesn't have the execute bit set.
- Insufficient resources available to create the child process.
- An error occurred duplicating open file descriptors to the new process.
- The mode is P_WAIT, and the spawned
process terminated before the call to waitpid() was completed.
- One of the buffers specified in the function call is invalid.
- The function was interrupted by a signal.
- An argument is invalid (e.g. arg0 is NULL, or
the value of mode isn't valid).
- Too many levels of symbolic links or prefixes.
- Insufficient resources available to load the new executable
image or to remap file descriptors in the child process.
- The length of file exceeds PATH_MAX or a
pathname component is longer than NAME_MAX.
- The file identified by the file argument is empty,
or one or more components of the pathname of the child process don't exist.
- The child process's file has the correct permissions, but isn't in the correct format for an executable.
- Insufficient memory available to create the child process.
- The spawnlpe() function isn't implemented for the filesystem specified in file.
- A component of the path prefix of the child process isn't a directory.
- The text file that you're trying to execute is busy (e.g. it might
be open for writing).
||Read the Caveats|
If mode is P_WAIT, this function is a cancellation point.
Processes and Threads
chapter of Getting Started with QNX Neutrino