查看文件是否已更改 [英] Find out if file has changed

问题描述

我想查明自上次启动我的 shell 脚本以来文件是否已被修改，可能是通过创建布尔值或其他方式...也许可以将上次运行脚本的时间保存在文本文件中，并且下次启动脚本时它应该读取该文件，然后它应该找出已更改的文件，以便我可以检查是否有文件已使用以下内容更改:

I want to find out if a file has been modified since the last time my shell script was started, maybe by creating a boolean or something... Maybe it would be possible to save the last time the script was run in a text file and when the script is started the next time it should read this file and then it should find out what file have been changed so that I can check if a file has changed using something like:

for file in *
do
    #Somecode here
    if [ $filehaschanged != "0" ]; then
    echo "Foobar" > file.txt
    fi
    #Somecode here
done

也许有可能用 find...有什么想法吗?

Maybe it would be possible to do this with find...any ideas?

推荐答案

Michael，通过changed"，您是在问文件是否已被触摸(即 datestamp 较新)，还是您在问内容是否不同?

Michael, by "changed", are you asking if the file has been touched (i.e. datestamp is newer), or are you asking if the content is different?

如果是前者，您可以使用 find 或 test 进行测试.例如在shell中:

If the former, you can test this with find or test. For example, in shell:

#!/bin/sh
touch file1
sleep 1
touch file2
if [ "file1" -nt "file2" ]; then
  echo "This will never be seen."
else
  echo "Sure enough, file1 is older."
fi

如果您要查找的内容是对内容的测试，那么您的操作系统可能包含将测试文件哈希的内容.

If what you're looking for is a test of the contents, then your operating system probably includes something that will test the hash of a file.

[ghoti@pc ~]$ date > testfile
[ghoti@pc ~]$ md5 testfile
MD5 (testfile) = 1b2faf8be02641f37e6d87b15444417d
[ghoti@pc ~]$ cksum testfile
3778116869 29 testfile
[ghoti@pc ~]$ sha1 testfile 
SHA1 (testfile) = 5f4076a3828bc23a050be4867549996180c2a09a
[ghoti@pc ~]$ sha256 testfile
SHA256 (testfile) = f083afc28880319bc31417c08344d6160356d0f449f572e78b343772dcaa72aa
[ghoti@pc ~]$ 

我在 FreeBSD.如果您使用的是 Linux，那么您可能使用的是md5sum"而不是md5".

I'm in FreeBSD. If you're in Linux, then you probably have "md5sum" instead of "md5".

要将其放入脚本中，您需要遍历文件列表，存储它们的哈希值，然后有一种机制来根据存储的哈希值测试当前文件.这很容易编写脚本:

To put this into a script, you'd need to walk through your list of files, store their hashes, then have a mechanism to test current files against their stored hashes. This is easy enough to script:

[ghoti@pc ~]$ find /bin -type f -exec md5 {} ; > /tmp/md5list
[ghoti@pc ~]$ head -5 /tmp/md5list
MD5 (/bin/uuidgen) = 5aa7621056ee5e7f1fe26d8abb750e7a
MD5 (/bin/pax) = 7baf4514814f79c1ff6e5195daadc1fe
MD5 (/bin/cat) = f1401b32ed46802735769ec99963a322
MD5 (/bin/echo) = 5a06125f527c7896806fc3e1f6f9f334
MD5 (/bin/rcp) = 84d96f7e196c10692d5598a06968b0a5

您可以将它存储在一个可预测的位置(而不是/bin 对任何重要的东西运行它，也许是 /)，然后编写一个快速脚本来检查一个文件的哈希值:

You can store this (instead of /bin run it against whatever's important, perhaps /) in a predictable location, then write a quick script to check a file against the hash:

#!/bin/sh

sumfile=/tmp/md5list

if [ -z "$1" -o ! -f "$1" ]; then
  echo "I need a file."
  exit 1
elif ! grep -q "($1)" $sumfile; then
  echo "ERROR: Unknown file: $1."
  exit 1
fi

newsum="`md5 $1`"

if grep -q "$newsum" $sumfile; then
  echo "$1 matches"
else
  echo "$1 IS MODIFIED"
fi

这种脚本是 tripwire 等工具提供的.

This kind of script is what tools like tripwire provide.

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