test?命令非常強大，但是很難滿足其轉(zhuǎn)義需求以及字符串和算術(shù)比較之間的區(qū)別。

大于	小于	等于	不等于
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”))

字符串比較

大于	小于	等于	不等于
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 []

功能	[[ ]]	[ ]	例子
字符串比較	>	\>	?-
	=(or ==)	=	?-
	!=	!=	?-
表達式組合	&&	-a	[[ -n $var && -f $var ]] && echo “$var is a file”
	||	-o	?-
模式匹配 (Pattern matching)	=(or ==)	木有	[[ $name = "a*" ]] -> the string “a*”
正則匹配(RegularExpression matching)	=~	木有	[[ $(date) =~ ^Fri\ ...\ 13 ]] && echo “It’s Friday the 13th!”

特性	?	例子
文件或文件夾存在	-e	[[?-e?$config?]]?&&?echo?”config?file?exists:?$config”
文件新舊比較	-nt/-ot	[[?$file0?-nt?$file1?]]?&&?echo?”$file0?is?newer?than?$file1″
同一個文件	-ef	[[?$input?-ef?$output?]] \?&&?{?echo?”will?not?overwrite?input?file:?$input”;?exit?1;?}?
否定	!	-

邏輯組合判斷的一些例子：
if [ $condition1 ] && [ $condition2 ]
if [ $condition1 -a $condition2 ]
if [[ $condition1 && $condition2 ]]
if [ $condition1 ] || [ $condition2 ]
if [ $condition1 -o $condition2 ]
if [[ $condition1 || $condition2 ]] # Also works.
#The &&, ||, operators work within a [[ ]] test, despite giving an error within a [ ] construct.

大于	小于	等于	不等于
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”))

字符串比較

大于	小于	等于	不等于
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 []

功能	[[ ]]	[ ]	例子
字符串比較	>	\>	?-
	=(or ==)	=	?-
	!=	!=	?-
表達式組合	&&	-a	[[ -n $var && -f $var ]] && echo “$var is a file”
	||	-o	?-
模式匹配 (Pattern matching)	=(or ==)	木有	[[ $name = "a*" ]] -> the string “a*”
正則匹配(RegularExpression matching)	=~	木有	[[ $(date) =~ ^Fri\ ...\ 13 ]] && echo “It’s Friday the 13th!”

特性	?	例子
文件或文件夾存在	-e	[[?-e?$config?]]?&&?echo?”config?file?exists:?$config”
文件新舊比較	-nt/-ot	[[?$file0?-nt?$file1?]]?&&?echo?”$file0?is?newer?than?$file1″
同一個文件	-ef	[[?$input?-ef?$output?]] \?&&?{?echo?”will?not?overwrite?input?file:?$input”;?exit?1;?}?
否定	!	-

邏輯組合判斷的一些例子：
if [ $condition1 ] && [ $condition2 ]
if [ $condition1 -a $condition2 ]
if [[ $condition1 && $condition2 ]]
if [ $condition1 ] || [ $condition2 ]
if [ $condition1 -o $condition2 ]
if [[ $condition1 || $condition2 ]] # Also works.
#The &&, ||, operators work within a [[ ]] test, despite giving an error within a [ ] construct.

總結(jié)

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