bash - Doubts with for loop in Unix -

sorry if sounds dumb i'm studying exam apply job (administrative one) , learnt java, php, python not unix scripts. can see it's similar php in structure , have many questions .

one of them loop, , why output b*?

for var in b*    echo $var done 

i tried code , terminal output b*, why code answer me text (in case, b*) or else happen?

a loop in shell scripting takes each whitespace separated string input , assigns variable given, , runs code once each value. in case b* input , $var assigned variable.

the shell perform expansion on input. basically, * acts wildcard part of file name. if have files beginning b in current directory, looped over:

$ ls bean.java bean.class readme.txt $ var in b*; echo $var; done bean.java bean.class 

if don't have files beginning b (so pattern b* doesn't match anything) pattern remain unexpanded:

$ rm bean.* $ ls readme.txt $ var in b*; echo $var; done b*