while
continuebreak
语法
while [ condition ]; do
commands
done
例子
# timer.sh 倒计时
#-----------------
#!/bin/bash
read -p "Enter an integer: " num
while (( num >= 0 )); do
clear
echo "Counter: $num"
num=$((num - 1))
sleep 1
done
clear
until
语法
until [ condition ]; do
commands
done
例子
#!/bin/bash
read -p "Enter an integer: " num
until (( num < 0 )); do
clear
echo "Timer: $num"
num=$((num - 1))
sleep 1
done
clear
循环和重定向
重定向 stdin
$ cat data.txt
0 0
2 6
1 5
5 1
4 9
2 5
2 9
3 8
6 3
6 1
$ ./multi.sh
0 x 0 = 0
2 x 6 = 12
1 x 5 = 5
5 x 1 = 5
4 x 9 = 36
2 x 5 = 10
2 x 9 = 18
3 x 8 = 24
6 x 3 = 18
6 x 1 = 6
#multi.sh
#-------------
#!/bin/bash
while read num1 num2; do
printf "$num1 x $num2 = %s\n" $(($num1 * $num2))
done < data.txt
管道
$ ./file_size.sh
Path: .
total 1.8M
admin.txt 4.0K
counter.sh 4.0K
data.txt 4.0K
django_projects.tar.gz 1.7M
file_size.sh 4.0K
multi.sh 4.0K
nginx.tar.gz 8.0K
ta_1.txt 4.0K
task_1.txt 4.0K
task_2.txt 4.0K
test 0
until_counter.sh 4.0K
#!/bin/bash
read -p "Path: " path
ls -sh $path | while read size filename; do
if [[ $size =~ total ]]; then
printf "$size $filename\n\n"
continue
fi
printf "%-26s %s\n" $filename $size
done
for
第一种格式
$ for i in $(seq 5); do echo $i; done
1
2
3
4
5
$ for i in {1..5}; do echo $i; done
1
2
3
4
5
第二种格式
$ for ((i=1; i <=5 ; i++)); do echo $i; done
1
2
3
4
5
如果没有文件匹配，会直接显示通配符
$ ls
file_a file_b file_c
$ for file in file_*; do echo $file; done
file_a
file_b
file_c
# 如果没有文件匹配，会直接显示通配符
$ for file in dir_*; do echo $file; done
dir_*
# 加一个 if 检查
for file in dir_*; do
if [ -e "$file" ]; then
echo $file
fi
done
打印文件最长的行
$ cat ./longest-line.sh
#!/bin/bash
read -e -p "File: " file
if [ -e "$file" ]; then
longest_line=""
size=0
while read line; do
line_size=$(echo "$line" | wc -c)
if ((line_size > size)); then
longest_line="$line"
size="$line_size"
fi
done < $file
printf "longest line: %s\n" "$longest_line"
printf "size: %s charater(s)\n" "$size"
else
echo "ERROR: No sush file - $file" >&2
exit 1
fi