fork(S)

Syntax

int fork ()

Description

• environment: see putenv(S), getenv(S), environ(S), exec(S)

• close-on-exec flag: see fcntl(S), exec(S)

• signal-handling settings (that is, SIG_DFL, SIG_IGN, SIG_HOLD, function address): see sigaction(S), signal(M), and signal(S)

• signal mask: see sigprocmask(S)

• profiling on/off status: see profil(S)

• nice value: see nice(S)

• all attached shared memory segments: see shmop(S)

• process group ID: see setpgid(S), setsid(S), setpgrp(S), getpgid(S), getpgrp(S)

• tty group ID: see tcsetpgrp(S), tcgetpgrp(S), exit(S)

• current working directory: see chdir(S), getcwd(S)

• root directory: see chroot(S)

• file mode creation mask: see umask(S)

• file size limit: see ulimit(S)

• real, effective, and saved user IDs: see setuid(S), getuid(S), geteuid(S), exec(S)

• real, effective and saved group IDs: see setgid(S), getgid(S), getegid(S), exec(S)

• login user ID: see setluid(S), getluid(S)

• supplemental groups: see setgroups(S), getgroups(S)

• controlling terminal

• The child process has a unique process ID: see getpid(S)

• The child process has a different parent process ID: see getppid(S)

• The child process has its own copy of the parent's file descriptors. Each of the child's file descriptors shares a common file pointer with the corresponding file descriptor of the parent.

• No signals are pending in the child: see sigpending(S)

• All semadj values are cleared: see semop(S)

• Process locks, text locks, and data locks are not inherited by the child: see plock(S), lock(S)

• The child process' tms structure is cleared (setting utime, stime, cutime, and cstime to 0): see times(S)

• The time left until an alarm clock or itimer signal is reset to 0: see alarm(S), setitimer(S), getitimer(S)

• Record locks set by the parent are not inherited by the child: see fcntl(S), locking(S), lockf(S)

The fork system call fails and no child process is created if one or more of the following is true:

[EAGAIN]

• The system-imposed limit on the total number of processes under execution would be exceeded.

• The system-imposed limit on the total number of processes under execution by a single user would be exceeded.

• The total amount of system memory available when reading via raw I/O is temporarily insufficient.

[EMFILE]

The shared data table would overflow.

[ENOMEM]

The process requires more space than the system can supply.

See also

Diagnostics

Standards conformance

X/Open Portability Guide, Issue 3, 1989 ;
IEEE POSIX Std 1003.1-1990 System Application Program Interface (API) [C Language] (ISO/IEC 9945-1) ;
and NIST FIPS 151-1 .