for,break,continue,exit

if后接的是命令
if rpm -q gcc && id tom||echo "sss"; &&如果前面的命令执行成功则执行&&后的命
令否则执行||后面的命令

for 遇空格或回车算一次
for i in tom jerry do
for i in *.sh
{1..10}相当于1 2 3 4 5 6 7 8 9 10
for i in {1..10}
seq -w 10 等宽09 10
seq 2 2 10 从2到10 每隔一个取一个数
for i in ‘<file‘do
for ((i=0; i<10;i++))
#--------------------------------------------------------
while ((i<=10));do
while true do   a=" " while [$a ];do 相当于while [ -n $a ] do while [ 1 ] d
o 死循环
cat file|while read a b c；do   每次读一行文件将参数（以空格分割）分别赋值

case "$c" in
10|20|30)

;;

for,break,continue,exit