SWI-Prolog -- exec/1

Documentation
- Reference manual
- Packages
  - SWI-Prolog C-library
    - library(unix): Unix specific operations
      - fork/1
      - fork_exec/1
      - exec/1
      - wait/2
      - kill/2
      - pipe/2
      - dup/2
      - detach_IO/1
      - detach_IO/0
      - prctl/1
      - sysconf/1

Availability::- use_module(library(unix)).(can be autoloaded)

exec(+Command)

Replace the running program by starting Command. Command is a callable term. The functor is the command and the arguments provide the command-line arguments for the command. Each command-line argument must be atomic and is converted to a string before passed to the Unix call execvp(). Here are some examples:

exec(ls('-l'))
exec('/bin/ls'('-l', '/home/jan'))

Unix exec() is the only way to start an executable file executing. It is commonly used together with fork/1. For example to start netscape on an URL in the background, do:

run_netscape(URL) :-
        (    fork(child),
             exec(netscape(URL))
        ;    true
        ).

Using this code, netscape remains part of the process-group of the invoking Prolog process and Prolog does not wait for netscape to terminate. The predicate wait/2 allows waiting for a child, while detach_IO/0 disconnects the child as a deamon process.