errors specified for the fork (2) and setsid (2). ATTRIBUTES For an explanation ... double-fork technique (i.e., fork (2), setsid (2), fork (2)) that is necessary to ensuredefinition of this constant. POSIX_SPAWN_SETSID (since glibc 2.26) If this flag ... process group in the session (see setsid (2)). The _GNU_SOURCE feature test macro mustdefinition of this constant. POSIX_SPAWN_SETSID (since glibc 2.26) If this flag ... process group in the session (see setsid (2)). The _GNU_SOURCE feature test macro mustPOSIX inventions. SEE ALSO setpgid (2), setsid (2), credentialsPOSIX inventions. SEE ALSO setpgid (2), setsid (2), credentials