Shell

文件运算符

文件运算符	描述
-b file	检测 file 是否为块设备文件
-c file	检测 file 是否为字符设备文件
-d file	检测 file 是否为目录
-e file	检测 file 是否存在
-f file	检测 file 是否存在为普通文件
-r file	检测 file 是否可读
-s file	检测 file 是否为空文件
-w file	检测 file 是否可写
-x file	检测 file 是否可执行
-L file	检测 file 是否符号链接

实例

a) 检测 /dev/sr0 是否为块设备文件。

f="/dev/sr0"
if [ -b "$f" ]
then
    echo "${f} is a block (buffered) special file."
else
    echo "${f} is not a block (buffered) special file."
fi

b) 检测 /dev/null 是否为字符设备文件。

f="/dev/null"
if [ -c "$f" ]
then
    echo "${file} is a character (unbuffered) special file."
else
    echo "${file} is not a character (unbuffered) special file."
fi

c) 检测 /etc 是否为目录。

f="/etc"
if [ -d "$f" ]
then
    echo "${file} is a directory."
else
    echo "${file} is not a directory."
fi

d) 检测 /etc/passwd 是否为普通文件。

f="/etc/passwd"
if [ -f "$f" ]
then
    echo "${file} is a regular file."
else
    echo "${file} is not a regular file."
fi

e) 检测 /bin/mail 是否为符合链接。

f="/bin/mail"
if [ -L "$f" ]
then
    echo "${file} is a symbolic link."
else
    echo "${file} is not a symbolic link."
fi

f) 检测 /etc/passwd 是否可读。

f="/etc/passwd"
if [ -r "$f" ]
then
    echo "${file} is readable."
else
    echo "${file} is not readable."
fi

g) 检测 /etc/passwd 是否可写。

f="/etc/passwd"
if [ -w "$f" ]
then
    echo "${file} is writable."
else
    echo "${file} is not writable."
fi

h) 检测 /etc/passwd 是否可执行。

f="/etc/passwd"
if [ -x "$f" ]
then
    echo "${file} is executable."
else
    echo "${file} is not executable."
fi

i) 检测 /etc/passwd 是否存在。

f="/etc/passwd"
if [ -e "$f" ]
then
    echo "${file} is existent."
else
    echo "${file} is nonexistent."
fi

j) 检测 /etc/passwd 是否为空。

f="/etc/passwd"
if [ -s "$f" ]
then
    echo "${file} is empty."
else
    echo "${file} is not empty."
fi