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Is double square brackets [[ ]] preferable over single square brackets [ ] in Bash?7个
这可能已经回答了,但无论如何我都会问它.我有两个版本的脚本(comp.sh) –
这可能已经回答了,但无论如何我都会问它.我有两个版本的脚本(comp.sh) –
#!/bin/sh export tDay=$(date '+%Y%m%d') newfile="filename_$tDay" filename="filename_20120821100002.csv" echo $newfile $filename if [ $filename = *$newfile* ] then echo "Matched" else echo "Not Matched!" fi Output: $./comp.sh filename_20120821 filename_20120821100002.csv Not Matched!
和
#!/bin/sh export tDay=$(date '+%Y%m%d') newfile="filename_$tDay" filename="filename_20120821100002.csv" echo $newfile $filename if [[ $filename = *$newfile* ]] then echo "Matched" else echo "Not Matched!" fi $comp.sh filename_20120821 filename_20120821100002.csv Matched
有人可以解释我为什么不同？
另外 – 在什么情况下应该使用[]而不是[[]],反之亦然？
test的字符串相等运算符不执行globs.
$[ abc = *bc ] ; echo $? 1 $[[ abc = *bc ]] ; echo $? 0
