|This version of this document is no longer maintained. For the latest documentation, see http://www.qnx.com/developers/docs.|
Spawn a child process, given a list of arguments, an environment, and a relative path
#include <process.h> int spawnlpe( int mode, const char * file, const char * arg0, const char * arg1..., const char * argn, NULL, 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 wait() 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*() function.
- 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 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 qcc 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 spawnvpe().
|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:
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. At least one argument, arg0, must be passed to the child process. By convention, this first argument is a pointer to the name of the new 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 environ 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:
|P_WAIT||The exit status of the child process.|
|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).
- 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.
- One of the buffers specified in the function call is invalid.
- 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.
|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(), spawnl(), spawnle(), spawnlp(), spawnp(), spawnv(), spawnve(), spawnvp(), spawnvpe(), wait(), waitpid()
Processes and Threads chapter of Getting Started with QNX Neutrino