判断文件是否存在的shell脚本代码

转载地址：http://www.jb51.net/article/34330.htm

-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！

实例代码：

#!/bin/sh
# 判断文件是否存在
# link：www.jb51.net
# date：2013/2/28
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

字符串比较运算符 （请注意引号的使用，这是防止空格扰乱代码的好方法）

-eq 等于

-ne 不等于

-gt 大于

-lt 小于

-le 小于等于

-ge 大于等于

-z 空串

= 两个字符相等

!= 两个字符不等

-n 非空串

-z string 如果 string 长度为零，则为真 [ -z $myvar ]

-n string 如果 string 长度非零，则为真 [ -n $myvar ]

string1 = string2 如果 string1 与 string2 相同，则为真 [ $myvar = one two three ]