This is a shell script training program, mainly to practice the use of for-in loop
#！ /bin/bash
for i in `seq 1 9` #The outer loop is responsible for printing the line... Note that `seq 1 9` is enclosed in backticks (not single quotes), indicating command substitution
do
for j in `seq 1 $i` #The inner loop is responsible for printing columns... In shell scripts, when using variables, you need to add a $ sign before the variable name
do #The boundary of the loop body, described by do and done
echo -ne ''$j*$i=$[$j*$i]\t" #$ is connected with [], which means arithmetic operation...because \t is an escape character, -e is needed, -n means cancel line feed (requires "striking")
done
echo #The role of this echo: After each memory cycle ends, a newline is performed (echo defaults to a newline)
done
Script execution effect
Script description:
There are two types of for statements in shell scripts:
one is a "traverser" (that is, a for-in loop), which is similar to the foreach statement in java. Before executing the loop, there must be a set. The process of loop execution is the process of variable set elements. ... This article introduces this
kind of "automatic machine", which is similar to the for loop in C language, and needs to describe the boundary and step size of the loop ... Next time I will introduce it