bash 检查有效链接（URL）
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Check for valid link (URL)
提问by Mint
I was reading though this other questionwhich has some really good regex's for the job but as far as I can see non of them work with BASH commands as BASH commands don't support such complex rexeg's.
我正在阅读另一个问题，该问题对这项工作有一些非常好的正则表达式，但据我所知，它们中没有一个可以使用 BASH 命令，因为 BASH 命令不支持如此复杂的正则表达式。
if echo "http://www.google.com/test/link.php" | grep -q '(https?|ftp|file)://[-A-Z0-9\+&@#/%?=~_|!:,.;]*[-A-Z0-9\+&@#/%=~_|]'; then
echo "Link valid"
else
echo "Link not valid"
fi
But this doesn't work as grep -q doesn't work ...
但这不起作用，因为 grep -q 不起作用......
Edit, ok I just realised that grep had an "extended-regex" (-E) option which seems to make it work. But if anyone has a better/faster way I would still love to here about it.
编辑，好吧，我刚刚意识到 grep 有一个“扩展正则表达式”（-E）选项，这似乎使它起作用。但是如果有人有更好/更快的方法，我仍然很乐意在这里讨论它。
回答by Paused until further notice.
The following works in Bash >= version 3.2 without using grep:
以下适用于 Bash >= 3.2 版，无需使用grep：
regex='(https?|ftp|file)://[-A-Za-z0-9\+&@#/%?=~_|!:,.;]*[-A-Za-z0-9\+&@#/%=~_|]'
string='http://www.google.com/test/link.php'
if [[ $string =~ $regex ]]
then
echo "Link valid"
else
echo "Link not valid"
fi
Your regex doesn't seem to include lowercase alpha characters [a-z]so I added them here.
您的正则表达式似乎不包含小写字母字符，[a-z]因此我在此处添加了它们。
回答by Patrick Steil
Since I don't have enough rep to comment above, I am going to amend the answer given by Dennis above with this one.
由于我没有足够的代表在上面发表评论，我将用这个来修改上面丹尼斯给出的答案。
I incorporated Christopher's update to the regex and then added more to it so that the URL has to at least be in this format:
我将 Christopher 的更新合并到正则表达式中，然后添加了更多内容，以便 URL 至少必须采用以下格式：
http://w.w(has to have a period in it).
http://ww（必须有句号）。
And tweaked output a bit :)
并稍微调整了输出:)
regex='^(https?|ftp|file)://[-A-Za-z0-9\+&@#/%?=~_|!:,.;]*[-A-Za-z0-9\+&@#/%=~_|]\.[-A-Za-z0-9\+&@#/%?=~_|!:,.;]*[-A-Za-z0-9\+&@#/%=~_|]$'
url='http://www.google.com/test/link.php'
if [[ $url =~ $regex ]]
then
echo "$url IS valid"
else
echo "$url IS NOT valid"
fi
回答by David Z
Probably because the regular expression is written in PCRE syntax. See if you have (or can install) the program pcregrepon your system - it has the same syntax as grepbut accepts Perl-compatible regexes - and you should be able to make that work.
可能是因为正则表达式是用 PCRE 语法编写的。查看pcregrep您的系统上是否有（或可以安装）该程序- 它的语法与grepPerl 兼容的正则表达式相同，但您应该能够使其工作。
Another option is to try the -Poption to grep, but the man page says that's "highly experimental" so it may or may not actually work.
另一种选择是尝试-P选择grep，但手册页说这是“高度实验性的”，因此它可能会也可能不会实际工作。
I will say that you should think carefully about whether it's really appropriate to be using this or any regex to validate a URL. If you want to have a correct validation, you'd probably be better off finding or writing a small script in, say, Perl, to use the URL validation facilities of the language.
我会说你应该仔细考虑使用这个或任何正则表达式来验证 URL 是否真的合适。如果您想进行正确的验证，您最好找到或编写一个小脚本，例如 Perl，以使用该语言的 URL 验证工具。
EDIT: In response to your edit in the question, I didn't notice that that regex is also valid in "extended" syntax. I don't think you can get better/faster than that.
编辑：为了回应您在问题中的编辑，我没有注意到该正则表达式在“扩展”语法中也有效。我认为你不能比这更好/更快。
