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Top Forums Shell Programming and Scripting what does echo $$, $? $# mean Post 302219729 by era on Wednesday 30th of July 2008 01:03:17 AM
Old 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)
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