Shell 实用技巧

判断文件是否存在

实现代码一

#!/bin/sh

myPath="/var/log/httpd/"
myFile="/var /log/httpd/access.log"
fsda1="/dev/sda1"

# 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-b 参数判磁盘块设备是否存在
if [ -b "$fsda1" ]; then
        echo  "Fond $fsda1"
else
        echo  "Not fond $fsda1"
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

实现代码二

#如果文件夹不存在，创建文件夹
if [ ! -d "/myfolder" ]; then
 mkdir /myfolder
fi

#shell判断文件,目录是否存在或者具有权限

folder="/var/www/"
file="/var/www/log"

# -x 参数判断 $folder 是否存在并且是否具有可执行权限
if [ ! -x "$folder"]; then
 mkdir "$folder"
fi

# -d 参数判断 $folder 是否存在
if [ ! -d "$folder"]; then
 mkdir "$folder"
fi

# -f 参数判断 $file 是否存在
if [ ! -f "$file" ]; then
 touch "$file"
fi

# -n 判断一个变量是否有值
if [ ! -n "$var" ]; then
 echo "$var is empty"
 exit 0
fi

# 判断两个变量是否相等
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！