# Predefined Constants

The following list of signals are supported by the Process Control functions. Please see your systems signal(7) man page for details of the default behavior of these signals.

Process Control constants
`WNOHANG` (int)
`WUNTRACED` (int)
`WCONTINUED` (int)
`WEXITED` (int)
`WSTOPPED` (int)
`WNOWAIT` (int)

SIG_* constants
`SIG_IGN` (int)
`SIG_DFL` (int)
`SIG_ERR` (int)
`SIGHUP` (int)
`SIGINFO` (int)
`SIGINT` (int)
`SIGQUIT` (int)
`SIGILL` (int)
`SIGTRAP` (int)
`SIGABRT` (int)
`SIGIOT` (int)
`SIGBUS` (int)
`SIGFPE` (int)
`SIGKILL` (int)
`SIGUSR1` (int)
`SIGSEGV` (int)
`SIGUSR2` (int)
`SIGPIPE` (int)
`SIGALRM` (int)
`SIGTERM` (int)
`SIGSTKFLT` (int)
`SIGCLD` (int)
`SIGCHLD` (int)
`SIGCONT` (int)
`SIGSTOP` (int)
`SIGTSTP` (int)
`SIGTTIN` (int)
`SIGTTOU` (int)
`SIGURG` (int)
`SIGXCPU` (int)
`SIGXFSZ` (int)
`SIGVTALRM` (int)
`SIGPROF` (int)
`SIGWINCH` (int)
`SIGPOLL` (int)
`SIGIO` (int)
`SIGPWR` (int)
`SIGSYS` (int)
`SIGBABY` (int)
`SIGRTMIN` (int)
`SIGRTMAX` (int)
`SIG_BLOCK` (int)
`SIG_UNBLOCK` (int)
`SIG_SETMASK` (int)
`SIGCKPT` (int)
  Generates/restores a checkpoint. Available from PHP 8.4.0 (DragonFlyBSD only).
`SIGCKPTEXIT` (int)
  Generates/restores a checkpoint and exit. Available from PHP 8.4.0 (DragonFlyBSD only).

SI_* constants
`SI_USER` (int)
`SI_NOINFO` (int)
`SI_KERNEL` (int)
`SI_QUEUE` (int)
`SI_TIMER` (int)
`SI_MSGGQ` (int)
`SI_ASYNCIO` (int)
`SI_SIGIO` (int)
`SI_TKILL` (int)
`SI_MESGQ` (int)

CLD_* constants
`CLD_EXITED` (int)
`CLD_KILLED` (int)
`CLD_DUMPED` (int)
`CLD_TRAPPED` (int)
`CLD_STOPPED` (int)
`CLD_CONTINUED` (int)

TRAP_* constants
`TRAP_BRKPT` (int)
`TRAP_TRACE` (int)

POLL_* constants
`POLL_IN` (int)
`POLL_OUT` (int)
`POLL_MSG` (int)
`POLL_ERR` (int)
`POLL_PRI` (int)
`POLL_HUP` (int)

ILL_* constants
`ILL_ILLOPC` (int)
`ILL_ILLOPN` (int)
`ILL_ILLADR` (int)
`ILL_ILLTRP` (int)
`ILL_PRVOPC` (int)
`ILL_PRVREG` (int)
`ILL_COPROC` (int)
`ILL_BADSTK` (int)

FPE_* constants
`FPE_INTDIV` (int)
`FPE_INTOVF` (int)
`FPE_FLTDIV` (int)
`FPE_FLTOVF` (int)
`FPE_FLTUND` (int)
`FPE_FLTRES` (int)
`FPE_FLTINV` (int)
`FPE_FLTSUB` (int)

SEGV_* constants
`SEGV_MAPERR` (int)
`SEGV_ACCERR` (int)

BUS_* constants
`BUS_ADRALN` (int)
`BUS_ADRERR` (int)
`BUS_OBJERR` (int)

CLONE_* constants
`CLONE_NEWNS` (int)
  Available as of PHP 7.4.0
`CLONE_NEWIPC` (int)
  Available as of PHP 7.4.0
`CLONE_NEWUTS` (int)
  Available as of PHP 7.4.0
`CLONE_NEWNET` (int)
  Available as of PHP 7.4.0
`CLONE_NEWPID` (int)
  Available as of PHP 7.4.0
`CLONE_NEWUSER` (int)
  Available as of PHP 7.4.0
`CLONE_NEWCGROUP` (int)
  Available as of PHP 7.4.0

PRIO_* constants
`PRIO_PGRP` (int)
`PRIO_USER` (int)
`PRIO_PROCESS` (int)
`PRIO_DARWIN_BG` (int)
  Available as of PHP 8.1.0.
`PRIO_DARWIN_THREAD` (int)
  Available as of PHP 8.1.0.

Constants | Description
--- | ---
Process Control error constants
`PCNTL_E2BIG` (int) | Argument list too long
`PCNTL_EACCES` (int) | Permission denied
`PCNTL_EAGAIN` (int) | Resource temporarily unavailable
`PCNTL_ECAPMODE` (int) | The process attempted an operation not permitted in capability mode while running in capability mode.
`PCNTL_ECHILD` (int) | No child processes
`PCNTL_EFAULT` (int) | Bad address
`PCNTL_EINTR` (int) | Interrupted function call
`PCNTL_EINVAL` (int) | Invalid argument
`PCNTL_EIO` (int) | Input/output error
`PCNTL_EISDIR` (int) | Is a directory
`PCNTL_ELIBBAD` (int) | Accessing a corrupted shared library.
`PCNTL_ELOOP` (int) | Too many levels of symbolic links
`PCNTL_EMFILE` (int) | Too many open files. Commonly caused by exceeding the `RLIMIT_NOFILE` resource limit. Can also be caused by exceeding the limit specified in /proc/sys/fs/nr_open.
`PCNTL_ENAMETOOLONG` (int) | Filename too long
`PCNTL_ENFILE` (int) | Too many open files in system. On Linux, this is probably a result of encountering the /proc/sys/fs/file-max limit.
`PCNTL_ENOENT` (int) | No such file or directory. Typically, this error results when a specified pathname does not exist, or one of the components in the directory prefix of a pathname does not exist, or the specified pathname is a dangling symbolic link.
`PCNTL_ENOEXEC` (int) | Exec format error
`PCNTL_ENOMEM` (int) | Not enough space/cannot allocate memory
`PCNTL_ENOSPC` (int) | No space left on device
`PCNTL_ENOTDIR` (int) | Not a directory
`PCNTL_EPERM` (int) | Operation not permitted
`PCNTL_ESRCH` (int) | No such process
`PCNTL_ETXTBSY` (int) | Text file busy
`PCNTL_EUSERS` (int) | Too many users

FORK_* constants
`FORK_NOSIGCHLD` (int)
`FORK_WAITPID` (int)

RF* constants
`RFCFDG` (int)
`RFFDG` (int)
`RFLINUXTHPN` (int)
`RFNOWAIT` (int)
`RFPROC` (int)
`RFTHREAD` (int)
`RFTSIGZMB` (int)

First argument to `waitid` (`idtype`)
`P_ALL` (int)
  Select any children.
`P_PID` (int)
  Select by process ID.
`P_PGID` (int)
  Select by process group ID.
`P_PIDFD` (int)
  Select by PID file descriptor. Specific to Linux (since Linux 5.4).
`P_UID` (int)
  Select by effective user ID. Specific to NetBSD and FreeBSD.
`P_GID` (int)
  Select by effective group ID. Specific to NetBSD and FreeBSD.
`P_SID` (int)
  Select by session ID. Specific to NetBSD and FreeBSD.
`P_JAILID` (int)
  Select by jail identifier. Specific to FreeBSD.

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