Spawn a child process, given a list of arguments and a relative path
Synopsis:
#include <process.h>
int spawnlp( int mode,
const char * file,
const char * arg0,
const char * arg1...,
const char * argn,
NULL );
Arguments:
- mode
- 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.
- file
- 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.
Library:
libc
Use the -l c option to
qcc
to link against this library.
This library is usually included automatically.
Description:
The spawnlp() function creates and executes a new child process,
named in file with NULL-terminated list of arguments in
arg0 … argn. This function calls
spawnvpe().
Note:
- In order to create a child process, your process must have the
PROCMGR_AID_SPAWN ability enabled.
For more information, see
procmgr_ability().
- 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
QNX Neutrino User's Guide.
The spawnlp() 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 spawnp().
For greater portability, use
posix_spawn().
Most of the spawn*() functions do a lot of work before
a message is sent to
procnto:
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, with some restrictions.
The inherited attributes always include any environment variables
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.
The inheritance of other attributes such as file descriptors depends on the mode argument:
If it's not P_OVERLAY, inheritance proceeds as though calling spawn() with fd_count
set to 0, fd_map set to NULL, and inherit->flags set to 0.
This means all of the parent's file descriptors are inherited by the child, except those created with O_CLOEXEC.
Note that side channels are not inherited, because they aren't considered file descriptors.
To understand how the flags setting of 0 affects the inheritance of other attributes, see the
inheritance structure description.
If flags is P_OVERLAY, inheritance proceeds as though calling the appropriate exec*()
function, which has the same inheritance policy as spawn(); the spawn() reference lists all of the
inherited attributes.
Note:
A parent/child relationship doesn't imply that the child process dies when the parent process dies.
Returns:
The spawnlp() function's return value depends on the mode argument:
mode |
Return value |
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).
Errors:
- E2BIG
- The number of bytes used by the argument list of the new child process
is greater than ARG_MAX bytes.
- EACCES
- 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.
- EAGAIN
- Insufficient resources available to create the child process.
- EBADF
- An error occurred duplicating open file descriptors to the new process.
- ECHILD
- The mode is P_WAIT, and the spawned
process terminated before the call to waitpid() was completed.
- EFAULT
- One of the buffers specified in the function call is invalid.
- EINTR
- The function was interrupted by a signal.
- EINVAL
- An argument is invalid (e.g., arg0 is NULL, or
the value of mode isn't valid).
- ELOOP
- Too many levels of symbolic links or prefixes.
- EMFILE
- Insufficient resources available to load the new executable
image or to remap file descriptors in the child process.
- ENAMETOOLONG
- The length of file exceeds PATH_MAX or a
pathname component is longer than NAME_MAX.
- ENOENT
- The file identified by the file argument is empty,
or one or more components of the pathname of the child process don't exist.
- ENOEXEC
- The child process's file has the correct permissions, but isn't in the correct format for an executable.
- ENOMEM
- Insufficient memory available to create the child process.
- ENOSYS
- The spawnlp() function isn't implemented for the filesystem
specified in file.
- ENOTDIR
- A component of the path prefix of the child process isn't a directory.
- EPERM
- The calling process doesn't have the required permission (see
procmgr_ability()),
or an underlying call to
mmap()
failed because it attempted to set PROT_EXEC for a region of memory covered by
an untrusted memory-mapped file.
- ETXTBSY
- The text file that you're trying to execute is busy (e.g., it might
be open for writing).
See also the errors for
ConnectAttach()
and
MsgSendvnc().
Classification:
QNX Neutrino
Safety: |
|
Cancellation point |
Read the Caveats |
Interrupt handler |
No |
Signal handler |
No |
Thread |
Yes |
Caveats:
If mode is P_WAIT, this function is a cancellation point.