4 ms·
The meaning of special dollar sign shell variables
- epety 11y ago$1, $2, $3, ... are the positional parameters. $@ is an array-like construct of all positional parameters, {$1, $2, $3 ...}. $* is the IFS expansion of all positional parameters, $1 $2 $3 .... $# is the number of positional parameters. $- current options set for the shell. $$ pid of the current shell (not subshell). $_ most recent parameter (or the abs path of the command to start the current shell immediately after startup). $IFS is the (input) field separator. $? is the most recent foreground pipeline exit status. $! is the PID of the most recent background command. $0 is the name of the shell or shell script.