Linux Getting Started--shell script Common information summary

$ default variable in 1.shell

　　

$n $ $ for the first argument, and $ for the second argument ... $# Number of command-line arguments the name of the current program               $? The return code of the previous command or function returns 0 for success $* with "parameter 1 parameter 2 ... "Format Save all parameters [email protected] with" parameter 1 "" Parameter 2 "... form to save all parameters $$ This program (process ID number) PID

2. Common parentheses Usage

string comparison　 use double brackets [ []]; arithmetic comparison with single brackets []--left and right spaces

arithmetic operations with double parentheses (()); Shell commands and output parentheses ()--left and right without spaces

　　full parentheses usage, reference : http://blog.csdn.net/ztf312/article/details/52317571

Linux Getting Started--shell script Common information summary