posixspawn

Posix_spawn is a POSIX standard API for creating new processes. It provides a single, high-level interface to start a program and is designed as a safer and potentially more efficient alternative to the traditional fork followed by exec. The API is implemented on many Unix-like systems and in standard C libraries.

Two forms exist: posix_spawn and posix_spawnp. posix_spawn uses an explicit path to the executable, while posix_spawnp searches for the executable on the PATH.

Prototype (typical C usage):

int posix_spawn(pid_t *restrict pid, const char *restrict path, const posix_spawn_file_actions_t *restrict file_actions, const posix_spawn_attr_t *restrict attrp, char *const argv[restrict], char *const envp[restrict]);

int posix_spawnp(pid_t *restrict pid, const char *restrict file, const posix_spawn_file_actions_t *restrict file_actions, const posix_spawn_attr_t *restrict attrp, char *const argv[restrict], char *const envp[restrict]);

The file_actions and attrp parameters describe actions and attributes for the new process. File actions may specify duplicating, opening, or closing file descriptors; attributes may set IDs, scheduling parameters, and other behavior at spawn.

Return values: On success, posix_spawn stores the child process ID in *pid (when pid is non-null) and returns 0. On failure, it returns a nonzero errno value and no child process is created.

Portability and usage: posix_spawn is mandated by POSIX, but actual support varies by system. Some platforms implement a comprehensive set of spawn attributes, while others provide a more limited subset. It is commonly used in multithreaded programs to avoid the race conditions associated with fork and exec.