bash bash中不区分大小写的字符串比较
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case insensitive string comparison in bash
提问by jjacobs
The following line removes the leading text before the variable $PRECEDING
以下行删除变量前的前导文本 $PRECEDING
temp2=${content#$PRECEDING}
But now i want the $PRECEDINGto be case-insensitive. This works with sed's Iflag. But i can't figure out the whole cmd.
但现在我希望$PRECEDING不区分大小写。这适用于sed'sI标志。但我无法弄清楚整个 cmd。
采纳答案by sampson-chen
Here's a way to do it with sed:
这是使用sed执行此操作的一种方法：
temp2=$(sed -e "s/^.*$PRECEDING//I" <<< "$content")
Explanation:
解释：
^.*$PRECEDING:^means start of string,.means any character,.*means any character zero or more times. So together this means "match any pattern from start of string that is followed by (and including) string stored in$PRECEDING.- The
Ipart means case-insensitive, thegpart (if you use it) means "match all occurrences" instead of just the 1st. - The
<<<notation is for herestrings, so you save anecho.
^.*$PRECEDING:^表示字符串的开始，.表示任意字符，.*表示任意字符零次或多次。因此，这意味着“匹配从字符串开头开始的任何模式，后跟（并包括）存储在$PRECEDING.- 该
I部分表示不区分大小写，该g部分（如果您使用它）表示“匹配所有出现”而不仅仅是第一个。 - 该
<<<符号用于herestrings，因此您保存了一个echo.
回答by Riot
No need to call out to sed or use shopt. The easiest and quickest way to do this (as long as you have Bash 4):
无需调用 sed 或使用 shopt。执行此操作的最简单快捷的方法（只要您有 Bash 4）：
if [ "${var1,,}" = "${var2,,}" ]; then
echo "matched"
fi
All you're doing there is converting both strings to lowercase and comparing the results.
您所做的就是将两个字符串都转换为小写并比较结果。
回答by glenn Hymanman
The only bash way I can think of is to check if there's a match (case-insensitively) and if yes, exclude the appropriate number of charactersfrom the beginning of $content:
我能想到的唯一 bash 方法是检查是否存在匹配（不区分大小写），如果匹配，则从 $content 的开头排除适当数量的字符：
content=foo_bar_baz
PRECEDING=FOO
shopt -s nocasematch
[[ $content == ${PRECEDING}* ]] && temp2=${content:${#PRECEDING}}
echo $temp2
Outputs: _bar_baz
输出： _bar_baz
回答by user8853220
your examples have context-switching techniques. better is (bash v4):
您的示例具有上下文切换技术。更好的是（bash v4）：
VAR1="HELLoWORLD"
VAR2="hellOwOrld"
if [[ "${VAR1^^}" = "${VAR2^^}" ]]; then
echo MATCH
fi
回答by Daniel Rich
If you don't have Bash 4, I find the easiest way is to first convert your string to lowercase using tr
如果您没有 Bash 4，我发现最简单的方法是首先使用将您的字符串转换为小写 tr
VAR1=HelloWorld
VAR2=helloworld
VAR1_LOWER=$(echo "$VAR1" | tr '[:upper:]' '[:lower:]')
VAR2_LOWER=$(echo "$VAR2" | tr '[:upper:]' '[:lower:]')
if [ "$VAR1_LOWER" = "$VAR2_LOWER" ]; then
echo "Match"
else
echo "Invalid"
fi
This also makes it really easy to assign your output to variables by changing your echo to OUTPUT="Match"& OUTPUT="Invalid"
这也使得通过将 echo 更改为OUTPUT="Match"&将输出分配给变量变得非常容易OUTPUT="Invalid"
