shell [ 命令的执行 算术扩展 / 参数扩展 / 参数处理 初步用法]

1, 算术扩展

#!/bin/bash

x=0
while [ "$x" -ne 10 ]; do
	echo $x
	x=$(($x+1))
done

exit 0

2, 参数扩展

#!/bin/bash

for i in 1 2 ; do
	mkdir ${i}_tmp
done

exit 0

3, 参数的处理

#!/bin/bash

unset foo
echo ${foo:-bar}

foo=fud
echo ${foo:-bar}

foo=/usr/local/X11/startx
echo ${foo#*/}
echo ${foo##*/}

bar=/usr/local/etc/local/networks
echo ${bar%local*}
echo ${bar%%local*}

exit 0

输出 ：
bar
fud
usr/local/X11/startx
startx
/usr/local/etc/
/usr/

改变格式，重定向

#!/bin/bash

for i in *.gif ; do
	cjpeg $i > ${i%%gif}jpg
done