Bash脚本迭代目录的内容，仅移动当前未由其他进程打开的文件

Question

I have people uploading files to a directory on my Ubuntu Server.

I need to move those files to the final location (another directory) only when I know these files are fully uploaded.

Here's my script so far:

#!/bin/bash

cd /var/uploaded_by_users

for filename in *; do

        lsof $filename

        if [ -z $? ]; then
          # file has been closed, move it           
        else
          echo "*** File is open. Skipping..."
        fi

done

cd -

However it's not working as it says some files are open when that's not true. I supposed $? would have 0 if the file was closed and 1 if it wasn't but I think that's wrong.

I'm not linux expert so I'm looking to know how to implement this simple script that will run on a cron job every 1 minute.

Answer 1

[ -z $? ] [ -z $? ] checks if $? is of zero length or not. Since $? will never be a null string, your check will always fail and result in else part being executed. You need to test for numeric zero, as below:

lsof "$filename" >/dev/null; lsof_status=$?
if [ "$lsof_status" -eq 0 ]; then
  # file is open, skipping
else
  # move it
fi

Or more simply (as Benjamin pointed out):

if lsof "$filename" >/dev/null; then
  # file is open, skip
else
  # move it
fi

Using negation, we can shorten the if statement (as dimo414 pointed out):

if ! lsof "$filename" >/dev/null; then
  # move it
fi

You can shorten it even further, using && :

for filename in *; do
  lsof "$filename" >/dev/null && continue  # skip if the file is open
  # move the file
done

Answer 2

You may not need to worry about when the write is complete, if you are moving the file to a different location in the same file system. As long as the client is using the same file descriptor to write to the file, you can simply create a new hard link for the upload file, then remove the original link. The client's file descriptor won't be affected by one of the links being removed.

cd /var/uploaded_by_users
for f in *; do
    ln "$f" /somewhere/else/"$f"
    rm "$f"
done