bash 如何使用 curl 检查文件是否下载
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How to check if the file is downloaded with curl
提问by ashishk
I am writing a shell script, I need to download 6 files from internet, In the script I have done it as
我正在编写一个 shell 脚本，我需要从互联网上下载 6 个文件，在脚本中我已经完成了
curl a
curl b
curl c
and so on
It works, but sometimes curl: (7) couldn't connect to hostfor some files in the middle of script for example, It will successfully download a but miss the file b with the above error and will download the file c. I would like to catch this error so that my code will execute with the successful download of all the files.
它可以工作，但有时curl: (7) couldn't connect to host对于脚本中间的某些文件，例如，它会成功下载a，但会因上述错误而错过文件b，并将下载文件c。我想捕获此错误，以便在成功下载所有文件后执行我的代码。
回答by Jahid
You can use a loop:
您可以使用循环：
while true; do
curl --fail b && break
done
The loop won't break until b is downloaded. You can make it a retry function which you can call if a download fails on the first try:
在下载 b 之前循环不会中断。您可以将其设置为重试函数，如果第一次尝试下载失败，您可以调用该函数：
retry(){
while true; do
curl --fail "" && break ||
echo "Download failed for url:
retrying..."
done
}
Then do this:
然后这样做：
curl --fail a || retry a
curl --fail b || retry b
curl --fail c || retry c
If you just want to silent the error messages then:
如果您只想使错误消息静音，则：
curl a 2>/dev/null
curl b 2>/dev/null
...
Or if you want to just detect the error then:
或者，如果您只想检测错误，则：
if ! curl --fail a; then
echo "Failed"
fi
or, a one liner:
或者，单班轮：
curl --fail a || echo Failed
If you want to exit after a failure and also show your own message:
如果您想在失败后退出并显示您自己的消息：
curl --fail a 2>/dev/null || { echo failed; exit 1; }
回答by Andrew White
You could chain them with &&...
你可以用&&...链接它们
curl --fail a && curl --fail b && curl --fail c...
Update: as @nwk pointed out below, we need to add --failto make curl fail on bad http codes.
更新：正如@nwk 在下面指出的，我们需要添加--fail以使 curl 在错误的 http 代码上失败。
回答by nwk
Put set -eat the beginning of the shell script and use curl --fail. E.g.,
放在set -eshell 脚本的开头并使用curl --fail. 例如，
#!/bin/sh
set -e
curl --fail http://example.com/a
curl --fail http://example.com/b
curl --fail http://example.com/c
The set -ewill make the script stop with an error on the first unsuccessful command (one with an exit status ≠ zero).
这set -e将使脚本在第一个不成功的命令（退出状态≠零）上出现错误而停止。
回答by randominstanceOfLivingThing
You can check the status of execution of the last command by looking at the $?shell variable.
Execute command below to check the status of the last command anything other 0 shall indicate an error.
您可以通过查看$?shell 变量来检查最后一条命令的执行状态。执行下面的命令以检查最后一个命令的状态，任何其他 0 表示错误。
echo $?
echo $?
curl a
if [ "$?" -gt 0 ]
then
echo "Error downloading file a. Exiting"
exit
fi
curl b
if [ "$?" -gt 0 ]
then
echo "Error downloading file b. Exiting"
exit
fi
...
A simple modified form after @andlrc suggestion:
@andlrc 建议后的简单修改形式：
if ! curl a ; then echo "Got error downloading a"; fi
if ! curl b ; then echo "Got error downloading b"; fi
if ! curl c ; then echo "Got error downloading c"; fi
回答by Andrew Wolfe
for file2get in a b c d; do do :; until curl --fail $file2get; done
对于 abcd 中的 file2get；渡渡鸟 ：; 直到 curl --fail $file2get; 完毕
Or add an iterator counter to prevent endless looping
或者添加一个迭代器计数器来防止无限循环
