Shell数字序列的用法

1. 使用seq

cadenwu@cadenwu-laptop:~/Templates/Bash$ cat loop1.sh
#!/bin/bash

# SYNOPSIS
# seq [OPTION]... LAST
# seq [OPTION]... FIRST LAST
# seq [OPTION]... FIRST INCREMENT LAST

# usage: seq LAST
echo "usage: seq LAST"
for i in $(seq 3)
do
    echo "$i"
done
echo

# usage: seq FIRST LAST
echo "usage: seq FIRST LAST"
for i in $(seq 2 5)
do
    echo "$i"
done
echo

# usage: seq FIRST INCREMENT LAST
echo "usage: seq FIRST INCREMENT LAST"
for i in $(seq 4 2 10)
do
    echo "$i"
done
echo

cadenwu@cadenwu-laptop:~/Templates/Bash$ ./loop1.sh
usage: seq LAST
1
2
3

usage: seq FIRST LAST
2
3
4
5

usage: seq FIRST INCREMENT LAST
4
6
8
10


2. 使用loop

cadenwu@cadenwu-laptop:~/Templates/Bash$ cat loop2.sh
#!/bin/bash

for ((i=3; i<=7; i++))
do
    echo "$i"
done


cadenwu@cadenwu-laptop:~/Templates/Bash$ ./loop2.sh
3
4
5
6
7

3. 大括号{..}

cadenwu@cadenwu-laptop:~/Templates/Bash$ cat loop3.sh
#!/bin/bash

for i in {1..5}
do
    echo $i
done
cadenwu@cadenwu-laptop:~/Templates/Bash$ ./loop3.sh
1
2
3
4
5