Shell Script if judgment file

-S file file is somefile 0 o'clock
[f]: Determines whether it is a file [-

X "/bin/ls"]: Determines whether/BIN/LS exists and has executable permissions

[-n "$var]": Judge $va 　　　　　R variable has a value

["$a" = "$b"]: To determine if $a and $b are equal-          

r file users can read as true-

W file users can write as true

-X file Users can execute true-

f file file for the normal file is true-D file for the directory is true-c file for the character special files for the true-B file file for the

block special file for the true-

s file is not the same as the true. C12/>-t file is true when the device specified by the filename descriptor (default 1) is a terminal