07-30-2008
The manual page for your shell documents these.
$$ is the PID of the current process.
$? is the return code of the last executed command.
$# is the number of arguments in $*
$* is the list of arguments passed to the current process
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wait(1) General Commands Manual wait(1)
NAME
wait - await process completion
SYNOPSIS
[pid]
DESCRIPTION
If no argument is specified, waits until all processes (started with of the current shell have completed, and reports on abnormal termina-
tions. If a numeric argument pid is given and is the process ID of a background process, waits until that process has completed. Other-
wise, if pid is not a background process, exits without waiting for any processes to complete.
Because the system call must be executed in the parent process, the shell itself executes without creating a new process (see wait(2)).
Command-Line Arguments
supports the following command line arguments:
The unsigned decimal integer process
ID of a command, whose termination is to wait for.
WARNINGS
Some processes in a 2-or-more-stage pipeline may not be children of the shell, and thus cannot be waited for.
SEE ALSO
csh(1), ksh(1), sh-posix(1), sh(1), wait(2).
STANDARDS CONFORMANCE
wait(1)