bash 有两种 for 语法，一种是类似于C语言的数值型语法，另一种是 for in 语法。
for in 的语法格式为：
for <variable name> in <a list of items>;do <some command> $<variable name>;done;
示例：
for name in joey suzy bobby;do echo $name;done for i in $(ls *.pdf); do
mv $i $(basename $i .pdf)_$(date +%Y%m%d).pdf
done for i in web{0..10} db{0..2} balance_{a..c};do echo $i;done
web0
web1
web2
web3
web4
web5
web6
web7
web8
web9
web10
db0
db1
db2
balance_a
balance_b
balance_c for i in web-{us,ca}-{0..3};do echo $i;done
web-us-0
web-us-1
web-us-2
web-us-3
web-ca-0
web-ca-1
web-ca-2
web-ca-3 $ cat somelist
first_item
middle_things
foo
bar
baz
last_item
$ for i in `cat somelist`;do echo "ITEM: $i";done
ITEM: first_item
ITEM: middle_things
ITEM: foo
ITEM: bar
ITEM: baz
ITEM: last_item $ for i in file{1..3};do for x in web{0..3};do echo "Copying $i to server $x"; scp $i $x; done; done
Copying file1 to server web0
Copying file1 to server web1
Copying file1 to server web2
Copying file1 to server web3
Copying file2 to server web0
Copying file2 to server web1
Copying file2 to server web2
Copying file2 to server web3
Copying file3 to server web0
Copying file3 to server web1
Copying file3 to server web2
Copying file3 to server web3https://www.redhat.com/sysadmin/bash-scripting-loops