SHELL点滴

1.Shell判断文件是否存在

 

#!/bin/sh
myPath="/var/log/httpd/"
myFile="/var /log/httpd/access.log"
# 这里的-x 参数判断$myPath是否存在并且是否具有可执行权限
if [ ! -x "$myPath" ]; then
mkdir "$myPath"
fi
 # 这里的-d 参数判断$myPath是否存在
 if [ ! -d "$myPath" ]; then
 mkdir "$myPath"
 fi

 # 这里的-f参数判断$myFile是否存在
 if [ ! -f "$myFile" ]; then
 touch "$myFile"
 fi
 # 其他参数还有-n,-n是判断一个变量是否是否有值
 if [ ! -n "$myVar" ]; then
 echo "$myVar is empty"
 exit 0
 fi

 # 两个变量判断是否相等
 if [ "$var1" = "$var2" ]; then
 echo '$var1 eq $var2'
 else
 echo '$var1 not eq $var2'
 fi
-f 和-e的区别 

Conditional Logic on Files 



-a file exists. 

-b file exists and is a block special file. 

-c file exists and is a character special file. 

-d file exists and is a directory. 

-e file exists (just the same as -a). 

-f file exists and is a regular file. 

-g file exists and has its setgid(2) bit set. 

-G file exists and has the same group ID as this process. 

-k file exists and has its sticky bit set. 

-L file exists and is a symbolic link. 

-n string length is not zero. 

-o Named option is set on. 

-O file exists and is owned by the user ID of this process. 

-p file exists and is a first in, first out (FIFO) special file or 

named pipe. 

-r file exists and is readable by the current process. 

-s file exists and has a size greater than zero. 

-S file exists and is a socket. 

-t file descriptor number fildes is open and associated with a 

terminal device. 

-u file exists and has its setuid(2) bit set. 

-w file exists and is writable by the current process. 

-x file exists and is executable by the current process. 

-z string length is zero. 


是用 -s 还是用 -f 这个区别是很大的！

2.Shell算术运算

 

$[1+2] #value:3

`expr 1 + 2` #value:3

$((1 + 2)) #value:3

 

3.遍历文件的每行数据

while read lines

do

echo $lines

done<filename#filename为文件名

 

4.提取行数据

awk语法：awk /pattern/{action} filename

awk简单用法

获取文件第一，列的数据:

awk '{print $1}' filename

 

5.显示日期格式为yyyyMMdd

date +%Y%m%d

 

6.Map通过key值排序的简单小例子

 

HashMap<String, String> map = new HashMap<String, String>();
map.put("2012-07-04", "2012-07-04");
map.put("2012-07-03", "2012-07-03");
map.put("2012-07-07", "2012-07-07");
map.put("2012-07-01", "2012-07-01");

Object[] key = map.keySet().toArray();
Arrays.sort(key);
for (int i = 0; i < key.length; i++) {
	System.out.println(map.get(key[i]));
}