vfork() — Create a new process

Standards

Format

#define _XOPEN_SOURCE_EXTENDED 1
#include <sys/types.h>
#include <unistd.h>

pid_t vfork(void);

General description

In all other respects, the child is identical to the parent. Because the child is a duplicate, it contains the same call to vfork() that was in the parent. Execution begins with this vfork() call, which returns a value of 0; the child then proceeds with normal execution.

The vfork() function is not supported from a multithread environment.

For more information on vfork() from a z/OS® perspective, refer to z/OS UNIX System Services Programming: Assembler Callable Services Reference.

You can use z/OS memory files from a z/OS UNIX program. However, use of the vfork() function from the program removes access from a hiperspace memory file for the child process. Use of an exec function from the program clears a memory file when the process address space is cleared.

Special behavior for C: For POSIX resources, vfork() behaves as just described. But in general, MVS™ resources that existed in the parent do not exist in the child. This is true for open streams in MVS data sets and assembler-accessed z/OS facilities, such as STIMERS. In addition, z/OS allocations (through JCL, SVC99, or ALLOCATE) are not passed to the child process.

Returned value

If successful, vfork() returns 0 to the child process and the process ID of the newly created child to the parent process.

Related information

• sys/types.h
• unistd.h
• alarm() — Set an alarm
• fcntl() — Control open file descriptors
• getrlimit() — Get current or maximum resource consumption
• nice() — Change priority of a process
• putenv() — Change or add an environment variable
• rexec() — Execute commands one at a time on a remote host
• semop() — Semaphore operations
• setlocale() — Set locale
• shmat() — Shared memory attach operation
• sigaction() — Examine or change a signal action
• signal() — Handle interrupts
• sigpending() — Examine pending signals
• sigprocmask() — Examine or change a thread
• stat() — Get file information
• system() — Execute a command
• times() — Get process and child process times
• ulimit() — Get or set process file size limits