Shell Small Problem Summary

Writing a script today meets a strange thing.

Variable A is defined

If [-a $a];then echo "exists"; else echo "not exists"; fi

Result output:

Exists

It's a blind moment, but it's going to change.

If [-a "$a"]

Of course, a here is a script input parameters, sometimes there may be no input parameters, so there may be undefined things happen

In addition, (exp,..)), Exp can be a C language statement, the variable is not $, but it can only be an integer, no floating-point number

Small knowledge, references:

Http://www.cnblogs.com/chengmo/archive/2010/10/19/1855577.html

http://blog.csdn.net/taiyang1987912/article/details/39551385

Shell Small Problem Summary