[bash] Condition Tests

Table 5-3. Arithmetic test operators

Test	Comparison
-lt	Less than
-le	Less than or equal
-eq	Equal
-ge	Greater than or equal
-gt	Greater than
-ne	Not equal

Table 5-2. File attribute operators

Operator	True if...
-a file	file exists
-d file	file exists and is a directory
-e file	file exists; same as -a
-f file	file exists and is a regular file (i.e., not a directory or other special type of file)
-r file	You have read permission on file
-s file	file exists and is not empty
-w file	You have write permission on file
-x file	You have execute permission on file, or directory search permission if it is a directory
-N file	file was modified since it was last read
-O file	You own file
-G file	file's group ID matches yours (or one of yours, if you are in multiple groups)
file1 -nt file2	file1 is newer than file2 [6]
file1 -ot file2	file1 is older than file2

^[6] Specifically, the -nt and -ot operators compare modification times of two files.

Table 5-1. String comparison operators

Operator	True if...
str1 = str2[4]	str1 matches str2
str1 != str2	str1 does not match str2
str1 < str2	str1 is less than str2
str1 > str2	str1 is greater than str2
-n str1	str1 is not null (has length greater than 0)
-z str1	str1 is null (has length 0)