Bash foreach 循环
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Bash foreach loop
提问by danidacar
I have an input (let's say a file). On each line there is a file name. How can I read this file and display the content for each one.
我有一个输入（比方说一个文件）。每行都有一个文件名。如何读取此文件并显示每个文件的内容。
回答by Greg Hewgill
Something like this would do:
像这样的事情会做：
xargs cat <filenames.txt
The xargsprogram reads its standard input, and for each line of input runs the catprogram with the input lines as argument(s).
该xargs程序读取它的标准输入，以及用于输入的每一行的运行cat与输入线作为参数（一个或多个）程序。
If you really want to do this in a loop, you can:
如果您真的想在循环中执行此操作，您可以：
for fn in `cat filenames.txt`; do
echo "the next file is $fn"
cat $fn
done
回答by Tom K. C. Chiu
"foreach" is not the name for bash. It is simply "for". You can do things in one line only like:
“foreach”不是 bash 的名称。它只是“为了”。您只能在一行中执行以下操作：
for fn in `cat filenames.txt`; do cat "$fn"; done
Reference: http://www.cyberciti.biz/faq/linux-unix-bash-for-loop-one-line-command/
参考：http: //www.cyberciti.biz/faq/linux-unix-bash-for-loop-one-line-command/
回答by dogbane
Here is a whileloop:
这是一个while循环：
while read filename
do
echo "Printing: $filename"
cat "$filename"
done < filenames.txt
回答by Paused until further notice.
xargs --arg-file inputfile cat
This will output the filename followed by the file's contents:
这将输出文件名，后跟文件内容：
xargs --arg-file inputfile -I % sh -c "echo %; cat %"
回答by paxdiablo
You'll probably want to handle spaces in your file names, abhorrent though they are :-)
您可能想要处理文件名中的空格，尽管它们是可恶的 :-)
So I would opt initially for something like:
所以我最初会选择类似的东西：
pax> cat qq.in
normalfile.txt
file with spaces.doc
pax> sed 's/ /\ /g' qq.in | xargs -n 1 cat
<<contents of 'normalfile.txt'>>
<<contents of 'file with spaces.doc'>>
pax> _
回答by Alan Dyke
cat `cat filenames.txt`
will do the trick
会做的伎俩
回答by Israel P
If they all have the same extension (for example .jpg), you can use this:
如果它们都具有相同的扩展名（例如 .jpg），您可以使用：
for picture in *.jpg ; do
echo "the next file is $picture"
done
(This solution also works if the filename has spaces)
（如果文件名有空格，此解决方案也适用）
