. file [argument …]
. (dot) runs a shell script in the current environment and then returns. Normally, the shell runs a command file in a child shell so that changes to the environment by such commands as cd, set, and trap are local to the command file. The . (dot) command circumvents this feature.
. ./file
This indicates that the
shell file you want to run is in the working directory. Also, the
file need not be executable, even if it is looked for on the PATH. If
you specify an argument list argument …, . (dot)
sets the positional parameters to the arguments while running the
shell script, then restores the invoker's positional parameters.
If no argument list is specified, the shell script has the same
positional parameters as the invoker. Any changes made to the positional
parameters (for example, by the set command)
in the shell script remain in effect when the . (dot)
command ends.See Localization for more information.
Otherwise, the exit status is the exit status of the last command run from the script.
POSIX.2, X/Open Portability Guide, UNIX systems.
cd, set, sh, trap