07-shell If condition test and comparison

If condition test common syntax

• Test < testing expressions >
• [< test expression >]
• [[< Test expression >]]
• (< test expression >))

Test command AND [] testing operator

• Test < testing expressions >
• [< test expression >]
  
  

(these two syntaxes are equivalent)

test operator	full Spell	Description
-D	Directory	File exists and is directory
-F	File	File exists and is a normal file
-E	Exist	File exists
-R	Read	File exists and is readable
-S	Size	File exists and file size is not 0
-W	Write	File exists and can be written
-X	Exexutable	File exists and is executable
-L	Link	File exists and is a linked file
F1-nt F2	Newer than	File f1 than file F2 new
F1-ot F2	Olderthan	File F1 F2 older than file
-N	Not zero	The length of the string is not 0
-Z	Zero	The length of the string is 0
S1 = s2		String 1 equals String 2
S1! = S2		String 1 is not equal to string 2
-eq	Equal	Equal
-ne	Not equal	Not equal
-gt	Greater than	Greater than
-ge	Greater equal	Greater than or equal
-lt	Less than	Less than
-le	Less equal	Less than or equal
-A	and	And
-O	Or	Or
!	Not	Non -

Example:

test -f /data/test.sh && echo true || echo false
[ -f /data/test.sh ] && echo true || echo false

• When testing a variable with [], the test result may be incorrect if the variable being tested does not have double quotes:

file1 = / etc / passwd
[-f "$ file1"] && echo 1 || echo 0

If it is a file entity path, the result of quoting is the same as unquoting:
[-f "/ etc / passwd"] && echo 1 || echo 0
[-f / etc / passwd] && echo 1 || echo 0

[[]] test operator

• [[< Test expression >]]

In [[]] you can use wildcards, etc. for pattern matching
[[! $ a = ~ [1-3]]] && echo 1 || echo 0

test operator	full Spell	Description
-D	Directory	File exists and is directory
-F	File files exist and are normal files
-E	Exist	File exists
-R	Read	File exists and is readable
-S	Size	File exists and file size is not 0
-W	Write	File exists and can be written
-X	Exexutable	File exists and is executable
-L	Link	File exists and is a linked file
F1-nt F2	Newer than	File f1 than file F2 new
F1-ot F2	Olderthan	File F1 F2 older than file
-N	Not zero	The length of the string is not 0
-Z	Zero	The length of the string is 0
S1 = s2		String 1 equals String 2
S1! = S2		String 1 is not equal to string 2
==/=	Equal	Equal
!=	Not equal	Not equal
>	Greater than	Greater than
>=	Greater equal	Greater than or equal
<	Less than	Less than
<=	Less equal	Less than or equal
&&	and	And
||	Or	Or
!	Not	Non -

(()) test operator

• (< test expression >))
  • Common use and calculation
  • For relational operations of integers, you can also use the Shell's Arithmetic operator (())

((3>2)) && echo 1 || echo 0
((3!=2&&5==5)) && echo 1 || echo 0

07-shell If condition test and comparison