Linux shell directives such as-D,-F,-E, and other judgment expressions

File comparison Operators
-e filename true if filename exists [-e/var/log/syslog]
-D filename True if filename is a directory [-d/tmp/mydir]
-F filename True if filename is a regular file [-f/usr/bin/grep]
-L filename True if filename is a symbolic link [-l/usr/bin/grep]
-R filename True if filename is readable [-r/var/log/syslog]
-W filename if filename is writable, true [-w/var/mytmp.txt]
-X filename is true if filename is executable [-l/usr/bin/grep]
Filename1-nt filename2 If filename1 is newer than filename2, then true [/tmp/install/etc/services-nt/etc/services]
Filename1-ot filename2 If filename1 is older than filename2, then true [/boot/bzimage-ot Arch/i386/boot/bzimage]
String comparison operators (note the use of quotation marks, which is a good way to prevent whitespace from disturbing the code)
-Z String True if string length is zero [-Z ' $myvar ']
-N String if string length is nonzero, true [-n ' $myvar ']
string1= string2 If string1 is the same as string2, then true ["$myvar" = "One of the three"]
string1!= string2 If string1 differs from string2, true ["$myvar"! = "one, three"]
Arithmetic comparison operators
Num1-eq num2 equals [3-eq $mynum]
Num1-ne num2 Not equal to [3-ne $mynum]
Num1-lt num2 less than [3-lt $mynum]
Num1-le num2 less than or equal to [3-le $mynum]
NUM1-GT num2 greater than [3-GT $mynum]
Num1-ge num2 greater than or equal to [3-ge $mynum]

Linux shell directives such as-D,-F,-E, and other judgment expressions