问题描述
这可能是一个shell脚本编程很简单的事情，但我pretty新的给它。我试图在一个shell脚本来执行下面的命令，并将输出保存到一个变量
This might be a very simple thing for a shell scripting programmer but am pretty new to it. I was trying to execute the below command in a shell script and save the output into a variable
inputfile=$(ls -ltr *.{PDF,pdf} | head -1 | awk '{print $9}')
当我从终端火，但是当通过shell脚本（SH）执行失败，命令工作正常。这是为什么命令失败，这是否意味着shell脚本不支持命令还是我做错了？另外我怎么知道，如果一个命令将在外壳或不工作？
The command works fine when I fire it from terminal but fails when executed through a shell script (sh). Why is that the command fails, does it mean that shell script doesn't support the command or am I doing it wrong? Also how do I know if a command will work in shell or not?
只是为了给你我的要求一瞥，我试图从特定目录中获取最旧的文件（我也希望确保大写和小写扩展处理）。是否有任何其他方式做到这一点？
Just to give you a glimpse of my requirement, I was trying to get the oldest file from a particular directory (I also want to make sure upper case and lower case extensions are handled). Is there any other way to do this ?
推荐答案
上面的命令将正常工作，只有当两个 *。PDF 和 * .PDF 文件在你当前的目录。
如果您想在一个目录，只有那些你应该考虑使用例如一个执行它。
The above command will work correctly only if BOTH *.pdf and *.PDF files are in the directory you are currently.If you would like to execute it in a directory with only one of those you should consider using e.g.:
inputfiles=$(find . -maxdepth 1 -type f \( -name "*.pdf" -or -name "*.PDF" \) | xargs ls -1tr | head -1 )
的注意的：上述命令不带新线，或者找到的文件一长串文件的工作。
NOTE: The above command doesn't work with files with new lines, or with long list of found files.
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