spawn()

The QNX OS spawn() function is similar to posix_spawn().

The spawn() function gives you control over the following:

• file descriptors
• process group ID
• signal mask
• ignored signals
• scheduling policy
• scheduling parameters (priority)
• maximum stack size
• runmask (for SMP systems)

The basic forms of the spawn() function are:

spawn()

Spawn with the explicitly specified path.

spawnp()

Search the current PATH and invoke spawn() with the first matching executable.

There's also a set of convenience functions that are built on top of spawn() and spawnp() as follows:

spawnl()

Spawn with the command line provided as inline arguments.

spawnle()

spawnl() with explicitly passed environment variables.

spawnlp()

spawnp() that follows the command search path.

spawnlpe()

spawnlp() with explicitly passed environment variables.

spawnv()

Spawn with the command line pointed to by an array of pointers.

spawnve()

spawnv() with explicitly passed environment variables.

spawnvp()

spawnv() that follows the command search path.

spawnvpe()

spawnvp() with explicitly passed environment variables.

When a process is spawn()'ed, the child process inherits the following attributes of its parent:

• process group ID (unless SPAWN_SETGROUP is set in inherit.flags)
• session membership
• real user ID and real group ID
• supplementary group IDs
• priority and scheduling policy
• current working directory and root directory
• file creation mask
• signal mask (unless SPAWN_SETSIGMASK is set in inherit.flags)
• signal actions specified as SIG_DFL
• signal actions specified as SIG_IGN (except the ones modified by inherit.sigdefault when SPAWN_SETSIGDEF is set in inherit.flags)

The child process has several differences from the parent process:

• Signals set to be caught by the parent process are set to the default action (SIG_DFL).
• The child process's tms_utime, tms_stime, tms_cutime, and tms_cstime are tracked separately from the parent's.
• The number of seconds left until a SIGALRM signal would be generated is set to zero for the child process.
• The set of pending signals for the child process is empty.
• File locks set by the parent aren't inherited.
• Per-process timers created by the parent aren't inherited.
• Memory locks and mappings set by the parent aren't inherited.

The child process can access the parent process's environment by using the environ global variable (found in <unistd.h>).

For more information, see the spawn() function in the C Library Reference.