spawnvpe()

Spawn a child process, given a vector of arguments, an environment, and a relative path

Synopsis:

#include <spawn.h>

int spawnvpe( int mode, 
              const char * file, 
              char * const argv[], 
              char * const envp[] );

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.

argv

A pointer to an argument vector. The value in argv[0] should represent the filename of the program that you're loading. The last member of argv must be a NULL pointer. The value of argv can't be NULL, and argv[0] can't be a NULL pointer, even if you're not passing any argument strings.

envp

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:

variable=value
  

that's used to define an environment variable.

Library:

libc

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

Description:

The spawnvpe() function creates and executes a new child process, named in file with the NULL-terminated list of arguments in the argv vector.

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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.

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The spawnvpe() function isn't a POSIX 1003.1 function, and isn't guaranteed to behave the same on all operating systems. It calls 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 procnto.

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>).

The following arguments are passed to the underlying call (spawnp()):

spawnvpe(mode, file, argv, envp)

• Map attribute flags.

  Create temporary attribute structure and set the flags member based on the mode:

  • 0 if mode = P_WAIT/P_NOWAIT
  • SPAWN_EXEC if mode = P_OVERLAY
  • SPAWN_NOZOMBIE if mode = P_NOWAITO
• Call spawnp(file, 0, 0, attr, argv, envp).

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A parent/child relationship doesn't imply that the child process dies when the parent process dies.

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Returns:

The spawnvpe() function's return value depends on the mode argument:

If an error occurs, -1 is returned (errno is set).

Errors:

E2BIG

The number of bytes used by the argument list or environment list of the new child process is greater than ARG_MAX bytes.

EACCESS

Search permission is denied for a directory listed in the path prefix of the new child process or the new child process 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.

EFAULT

One of the buffers specified in the function call is invalid.

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 plus its path 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 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 spawnvpe() 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.

Classification:

QNX 4

Caveats:

If mode is P_WAIT, this function is a cancellation point.

See also:

execl(), execle(), execlp(), execlpe(), execv(), execve(), execvp(), execvpe(), getenv(), putenv(), setenv(), spawn(), spawnl(), spawnle(), spawnlp(), spawnlpe(), spawnp(), spawnv(), spawnve(), spawnvp(), wait(), waitpid()

Processes and Threads chapter of Getting Started with QNX Neutrino