shell判断文件或者文件夹是否存在

#!/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！