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2.7 KiB
Name
posix_spawn - launch a new process
Synopsis
#include <spawn.h>
int posix_spawn(pid_t* pid, const char* executable_path, const posix_spawn_file_actions_t*, const posix_spawnattr_t*, char* const argv[], char* const envp[]);
int posix_spawnp(pid_t* pid, const char* executable_path, const posix_spawn_file_actions_t*, const posix_spawnattr_t*, char* const argv[], char* const envp[]);
Description
Spawn a new process reading the binary executable_path, passing argv as arguments to main() and setting envp as argument.
Places the process ID of the new process in pid.
If executable_path passed to posix_spawn is a relative path, it is resolved relative to the current working directory.
If executable_path passed to posix_spawnp is a relative path, it is resolved by searching through directories specified in the PATH environment variable.
The posix_spawn_file_actions_t and posix_spawnattr_t arguments may be nullptr. If they aren't, see posix_spawn_file_actions(2) and posix_spawnattr(2) for what they do.
The last entry in argv and envp has to be nullptr.
The new process is started as if the following steps are executed in this order:
- A new process is started as if
fork()was called. - If the
posix_spawnattr_tparameter is non-nullptr, it takes effect. - If the
posix_spawn_file_actions_tparameter is non-nullptr, it takes effect. executable_pathis loaded and starts running, as ifexecveorexecvpewas called.
Return value
If the process is successfully forked, returns 0.
Otherwise, returns an error number. This function does not return -1 on error and does not set errno like most other functions, it instead returns what other functions set errno to as result.
If the process forks successfully but spawnattr or file action processing or exec fail, posix_spawn returns 0 and the child exits with exit code 127.
Example
This simple example launches /bin/Calculator.
To make the child process use the parent's environment, it passes environ from unistd.h.
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <spawn.h>
int main()
{
const char* argv[] = { "Calculator", nullptr };
pid_t child_pid;
if ((errno = posix_spawn(&child_pid, "/bin/Calculator", nullptr, nullptr, const_cast<char**>(argv), environ)))
perror("posix_spawn");
}