这些古怪的符号，其实都是有含义有规律的。弄懂它们一点都不难，只需要写点代码，运行一下就知道了。perl 的特殊变量更多，perldoc perlvar.
#/bin/bash # http://www.gnu.org/software/bash/manual/html_node/Special-Parameters.html # run it like # ./spec_para.sh 1 2 3 # Parameters echo $_ # absolute pathname echo $0 # ./spec_para.sh echo $1 # 1 echo $2 # 2 echo $3 # 3 # $* and $@ is differents echo $@ # 1 2 3 ("$1" "$2" "$3") echo $* # 1 2 3 ("$1c$2c$3") # c is the first character of the value of the IFS variable. If IFS is # unset, the parameters are separated by spaces. If IFS is null, the # parameters are joined without intervening separators. echo $# # 3 ( number of positional parameters in decimal ) echo $? # exit status of the most recently executed foreground pipeline echo $$ # process ID of the shell echo $! # process ID of the most recently executed background command echo $- # current option flags