Measuring open road seventy-seven: if shell's, case, for, while

 

Select statement (if statement)

Greater than: -gt
determines whether a directory exists: -d

if [Condition judging]; the then
　　statement1
　　statement2
elif [Analyzing conditions]; the then
　　statement1
　　statement2
.......
the else
　　of statement3 in the
　　statement4
Fi

Determine whether there is a directory, if present, to delete, if you do not exist, create

 

 

Branch statement (case statement)

case 值 in
val1)
    command1
    command2
    ...
    commandN ;;
val2）
    command1
    command2
    ...
    commandN ;;
esac

 

for loop

Shell used in the mathematical expression: ((mathematical expression))
expr, evaluates an expression value, which is similar to the python eval

 for var in list
do
　　commands
done

 

 

 $ (Seq 1 10): generating a sequence of 1--10, shell where for i in $ (seq 1 10) and the python for i in range (1,11) as

for i in $(seq 1 10)
do
    echo $(expr $i \* 3 + 1);
done

 

$@ 传递给脚本或函数的所有参数。

 

打印乘法口诀表

 

while循环

while argument;
do
    statement ...
done

 

统计目录下所有文件的行数之和

find . -type f：选出当前目录下所有的文件类型，去除文件夹

xargs：把接收到的参数(默认根据换行符或者空格)分割成一个个的参数

用cat显示每一个文件的内容

 

用wc -l统计文件的行数

 

最后的指令为：find . -type f | xargs cat | wc -l