in reply to Copying a list of files from a directory to a new directory

ramjamman:

If you're on a *NIX box and have a text file containing a list of files to copy to a new location, you don't even need to use perl to do the copy. Instead, you can use xargs and tar to do the job. As an example, here's a text file with a list of files to copy:

$ cat mylist.txt
foo
bar
bim/bam

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And in our source directory, we have the specified files, along with a file we want to ignore:

$ ls -alR source
source:
total 3.0K
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:51 ./
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:49 ../
-rw-r--r--  1 Roboticus None 4 Jul 21 00:47 bar
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:48 bim/
-rw-r--r--  1 Roboticus None 8 Jul 21 00:47 foo
-rw-r--r--  1 Roboticus None 7 Jul 21 00:51 ignore

source/bim:
total 1.0K
drwxr-xr-x+ 1 Roboticus None  0 Jul 21 00:48 ./
drwxr-xr-x+ 1 Roboticus None  0 Jul 21 00:51 ../
-rw-r--r--  1 Roboticus None 13 Jul 21 00:48 bam

[download]

At this time, our dest directory doesn't have anything interesting in it:

$ ls -alR dest
dest:
total 0
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:51 ./
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:49 ../

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So all we need to do is to start a process, change to the source directory and then use xargs to tell tar which files to copy into an archive. Then we'll pipe that archive to another process wherein we change to the destination directory and extract all the files, like this:

$ (cd source; xargs <../mylist.txt tar cf -) | (cd dest; tar xf -)

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After running that, the files we wanted to copy to dest are there:

$ ls -alR dest
dest:
total 2.0K
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:52 ./
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:49 ../
-rw-r--r--  1 Roboticus None 4 Jul 21 00:47 bar
drwxr-xr-x+ 1 Roboticus None 0 Jul 21 00:52 bim/
-rw-r--r--  1 Roboticus None 8 Jul 21 00:47 foo

dest/bim:
total 1.0K
drwxr-xr-x+ 1 Roboticus None  0 Jul 21 00:52 ./
drwxr-xr-x+ 1 Roboticus None  0 Jul 21 00:52 ../
-rw-r--r--  1 Roboticus None 13 Jul 21 00:48 bam

[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.

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Re^2: Copying a list of files from a directory to a new directory
by Laurent_R (Canon) on Jul 21, 2018 at 10:50 UTC
    Yes, roboticus++, you're right, a one-line shell command at the prompt is sufficient for the task at hand.

    But not being a great fan of the shell syntax, I would personally tend to do it with a Perl one-liner, something like this (reusing here the OP's syntax): 

    perl -ne 'chomp; system("cp $_ newdirectory/")' mylist.txt

    [download]
    even though it might be slightly less efficient, or possibly something similar using the File::Copy module.

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Re^2: Copying a list of files from a directory to a new directory
by soonix (Chancellor) on Jul 21, 2018 at 17:15 UTC

    The -f - is redundant, AFAIK. Then, newer (at least GNU) tar has a -T option (or --files-from) which eliminates the need for xargs, and a -C option (or --directory) which eliminates the need for cd and the parentheses

    This simplifies the script to 
    tar c -C source -T mylist.txt | tar xC dest

    [download]
    (Tested with MinGW on Win7)

    Of course, your script could be written right out of your head, while I had to open the man page for looking up the letter of that filelist option...

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      soonix:

      Heh, heh! In fact, when I was writing that response, I thought that tar would have such an option. But after listing through the first three or so pages of the dox, I got tired of looking. Then I thought I'd just xargs to convert the file into a list of command-line arguments. I nearly wrote it as cat mylist.txt | xargs | ... but didn't want to earn another "useless use of cat" award, so I just used xargs <mylist.txt to do the task.

      After your response, I again looked at man tar and found the option ... on the thirteenth page! Since my terminal is 57 lines long, that seems a bit excessive. I'm thinking that the man page for tar ought to be rearranged a bit, as that sounds like an option that's generally useful, and there are quite a few options that seem to be much more specialized, and hence useful in fewer situations. (I've never needed --hole-detection or --check-device both of which are on page 4.) Now that I'm aware of -T, though, I'll hopefully remember it for the next time. ;^)

      ...roboticus

      When your only tool is tar, all problems look like you're gonna have to read "War and Peace", possibly several times.

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Re^2: Copying a list of files from a directory to a new directory
by ramjamman (Sexton) on Jul 21, 2018 at 09:52 UTC

    The wisdom available here never ceases to impress me !!

     Thank you so much for your replies
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