[Reprinted] shell condition test

Original article address

: Http://blog.chinaunix.net/space.php? Uid = 1, 12077574

File status test
-B filename: returns true if filename exists and is a block file (0 is returned)
-C filename: returns true if filename exists and is a character file.
-D pathname: returns true if pathname exists and is a directory.
-E pathname: returns true if a file or directory specified by pathname exists.
-F filename: returns true if filename exists and is a regular file.
-G pathname: returns true if the file or directory specified by pathname exists and the sgid bit is set.
-H filename: returns true (or-l filename) If filename exists and is a symbolic link file)
-K pathname: returns the true value when the file or directory specified by pathname exists and the "Sticky" bit is set.
-P filename: returns true if filename exists and is a named pipe.
-R pathname: returns true if the file or directory specified by pathname exists and is readable.
-S filename: returns true if filename exists and the file size is greater than 0
-S filename: returns true if filename exists and is a socket
-T fd: returns true when FD is a file descriptor associated with the terminal device.
-U pathname: returns true if the file or directory specified by pathname exists and SUID bit is set.
-W pathname: returns true if a file or directory specified by pathname exists and can be written.
-X pathname: returns the true value when the file or directory specified by pathname exists and is executable.
-O pathname: returns true if the pathname exists and is owned by the user ID of the current process)
-G pathname: returns the true value when the user group of a user whose pathname exists and belongs to the valid user ID of the current process.
File1-nt file2: true when file1 is greater than file2
File1-ot file2: file1 returns true when file1 is earlier than file2
Example: If [-B/dev/hda]; then Echo "yes"; else echo "no"; Fi // print Yes
Test-C/dev/hda; echo $? // Print 1 to indicate that the return value of the test command is 1, And/dev/hda is not a character device.
[-W/etc/passwd]; echo $? // Check whether the passwd file is writable for the current user

Logical operators during testing
-Logic A and the operators are true on both sides, and the result is true. Otherwise, the result is false.
-O logic or, if either side of the operator is true, the result is true. Otherwise, the result is false.
! Logical No. The condition is false and the result is true.
Example: [-W result.txt-a-W score.txt]; echo $? // Test whether two files can be written.

Common string tests
-Z string: returns true if string is an empty string (0 in length ).
-N string: returns true if the string is a non-empty string.
Str1 = str2: returns true if the string str1 is equal to the string str2
Str1! = Str2: returns true if str1 and str2 are not equal.
Str1 <str2: sort in alphabetical order. str1 is prior to str2.
Str1> str2: sort in alphabetical order. str1 is placed after str2.
Example: name = "zqf"; [$ name = "zqf"]; echo $? // Print 0 to indicate that the variable name value is equal to the string "zqf"

Common numerical tests
Int1-EQ int2: If int1 is equal to int2, true is returned.
Int1-ne int2: If int1 is not equal to int2, true is returned.
Int1-lt int2: If int1 is smaller than int2, true is returned.
Int1-Le int2: If int1 is smaller than or equal to int2, true is returned.
Int1-GT int2: If int1 is greater than int2, true is returned.
Int1-ge int2: If int1 is greater than or equal to int2, true is returned.
Example: x = 1; [$ X-EQ 1]; echo $? // Print 0 to indicate that the value of variable X is equal to the number 1
X = A; [$ X-EQ "1"] // The shell prints the error message [: A: integer expression expected