Shell中判断文件、目录是否存在

-e filename 如果 filename存在，则为真 
-d filename 如果 filename为目录，则为真 
-f filename 如果 filename为常规文件，则为真 
-L filename 如果 filename为符号链接，则为真 
-r filename 如果 filename可读，则为真 
-w filename 如果 filename可写，则为真 
-x filename 如果 filename可执行，则为真 
-s filename 如果文件长度不为0，则为真 
-h filename 如果文件是软链接，则为真

-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.

#shell判断文件夹是否存在
#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