BASH shell test condition tests [[]] and [] similarities and differences summary

The test command is very powerful, but it is difficult to satisfy its escape requirements and the difference between string and arithmetic comparisons.

Greater than	Less than	Equals	Not equal to
If ["$a"-gt "$b"]	If ["$a"-lt "$b"]	If ["$a"-eq "$b"]	If ["$a"-ne "$b"]
if [["$a"-gt "$b"]]	if [["$a"-lt "$b"]]	if [["$a"-eq "$b"]]	if [["$a"-ne "$b"]]
if (("$a" > "$b"))	if (("$a" < "$b"))	if (("$a" = "$b"))	if (("$a"!= "$b"))

String comparisons

Greater than	Less than	Equals	Not equal to
If ["$a" \> "$b"]	If ["$a" \< "$b"]	If ["$a" = "$b"] If ["$a" = "$b"]	If ["$a"!= "$b"]
if [["$a" > "$b"]]	if [["$a" < "$b"]]	if [["$a" = "$b"]] if [["$a" = "$b"]]	if [["$a"!= "$b"]]

[[]] and []

Function	[[ ]]	[ ]	Example
String comparisons	>	\>	-
= (or = =)	=	-
!=	!=	-
An expression combination	&&	-A	[[-N $var &&-F $var]] && echo "$var is a file"
||	-O	-
Pattern matching (Pattern matching)	= (or = =)	Wood has	[[$name = "A *"]]-> the string "A *"
Regular match (regularexpression matching)	=~	Wood has	[[$ (date) =~ ^fri\]] && echo "It s Friday the 13th!"

-nt/-ot

Attribute		Example
File or folder exists	-e	[[ -e  $config  ]] &&&N bsp;echo  "config file exists:  $config"
File New and old comparison	[[  $file 0 -nt  $file 1 ]] && echo  "$file 0  is newer than  $file 1″
Same file	-ef td>	[[  $input  -ef  $output  ]] \ && { echo  "will not& nbsp;overwrite input file:  $input "; exit 1; }
Negative	!	-

Some examples of

Logical combination judgments:
If [$condition 1] && [$condition 2]
If [$condition 1-a $condition 2]
If [$condi Tion1 && $condition 2]]
If [$condition 1] | | [$condition 2]
If [$condition 1-o $condition 2]
If [[$condition 1 | | | $condition 2]] # Also works.
#The &&, | | |, operators work within a [[]] test, despite giving an error within a [] construct.

Greater than	Less than	Equals	Not equal to
If ["$a"-gt "$b"]	If ["$a"-lt "$b"]	If ["$a"-eq "$b"]	If ["$a"-ne "$b"]
if [["$a"-gt "$b"]]	if [["$a"-lt "$b"]]	if [["$a"-eq "$b"]]	if [["$a"-ne "$b"]]
if (("$a" > "$b"))	if (("$a" < "$b"))	if (("$a" = "$b"))	if (("$a"!= "$b"))

String comparisons

Greater than	Less than	Equals	Not equal to
If ["$a" \> "$b"]	If ["$a" \< "$b"]	If ["$a" = "$b"] If ["$a" = "$b"]	If ["$a"!= "$b"]
if [["$a" > "$b"]]	if [["$a" < "$b"]]	if [["$a" = "$b"]] if [["$a" = "$b"]]	if [["$a"!= "$b"]]

[[]] and []

Function	[[ ]]	[ ]	Example
String comparisons	>	\>	-
= (or = =)	=	-
!=	!=	-
An expression combination	&&	-A	[[-N $var &&-F $var]] && echo "$var is a file"
||	-O	-
Pattern matching (Pattern matching)	= (or = =)	Wood has	[[$name = "A *"]]-> the string "A *"
Regular match (regularexpression matching)	=~	Wood has	[[$ (date) =~ ^fri\]] && echo "It s Friday the 13th!"

attribute		Example /strong>
File or folder exists	E	[ -e  ; $config  ]] && echo  "config file exists:  $config"
File old and new comparison	-nt/-ot	[[  $file 0 -nt  $file 1 ]] && echo  "$file 0 is newer  than  $file 1″
Same file	-ef	[[   $input  -ef  $output  ]] \ && { echo  "will not  overwrite input file:  $input "; exit 1; }
Deny	!	-

Some examples of

logical combination judgments:
If [$condition 1] && [$condition 2]
If [$condition 1-a $condition 2 ]
If [$condition 1 && $condition 2]]
If [$condition 1] | | [$condition 2]
If [$condition 1-o $condition 2]
If [[$condition 1 | | | $condition 2]] # Also works.
#The &&, | | |, operators work within a [[]] test, despite giving an error within a [] construct.