for DEMO

举例一：

[xiluhua@vm-xiluhua][~/shell_script]$ cat forDemo1.sh
#=======================================================================================
#/bin/bash
#auth: xiluhua
#date:
#desc: print file list in a directory
#=======================================================================================

[ -z $ ] && echo "exception@1: directory can not be null" && exit 

echo "prompt: print file list in a directory ..."
for file in $(ls $/*.123)
do
        echo $file
done
exit 0

举例二：

[xiluhua@vm-xiluhua][~/shell_script]$ cat forDemo2.sh
#=======================================================================================
#/bin/bash
#auth: xiluhua
#date:
#desc: print triangle with *
#=======================================================================================

for (( i=; i<; i++ ))
do
    let space=-$i
        #echo $space
        for (( j=; j<${space}; j++ ))
        do
                printf " "
        done

        let star=*$i+
        for (( k=; k<$star; k++ ))
    do
        printf "*"
    done

        echo ""
done