判断文件是否为bash中的PDF [英] Tell if a file is PDF in bash

问题描述

我需要编写一个bash脚本来判断文件是否为pdf文件.但是，我不能简单地使用文件名或扩展名.

I need to write a bash script to tell if a file is a pdf file. However, I cannot simply use the file name or extension.

例如:

test.pdf.encrypt-由于文件本身已加密并且文件属于计算机无法识别的未知类型，因此无法打开.

test.pdf.encrypt - will not open as the file itself is encrypted and the file is of an unknown type the computer can't recognize.

test.pdf.decrypt-即使扩展名为.decrypt

test.pdf.decrypt - will open even though the extension is .decrypt

由于查看扩展名无济于事，并且加密和解密文件的名称中间都带有.pdf，是否有办法进行系统测试，并查看该文件是否甚至可以用pdf阅读器读取?

As looking at the extension does not help and both the encrypted and decrypted file have .pdf in the middle of the name, is there a way to have the system test and see if the file is even readable with a pdf reader?

我只需要可以在bash中的if语句中输入的命令.

I just need the command that I can input into an if statement in bash.

if [this file is a working pdf file]; do
   echo "$file is a working pdf file."
fi

推荐答案

每个PDF文件均以％PDF 开头.您可以比较指定文件的前4个字符，以确保它是PDF.

Every PDF file starts with %PDF. You can compare the first 4 characters of a specified file in order to make sure it's a PDF.

FILE="/Users/Tim/Documents/My File.pdf"
if [ $(head -c 4 "$FILE") = "%PDF" ]; then
    echo "It's a PDF!"
fi

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