Ubuntu – Copy specific text from a multiple line file and paste it in another file automatically using terminal

Unfortunately the find command's -name predicate only accepts a single pattern. If you want to search for multiple files by name you'd need to chain them with the -o (logical OR) operator - something like:

find Documents/ \( -name "file2.txt" -o -name "file5.txt" -o -name "file9.txt" \) -print

This makes it tricky to construct the search programmatically from a list; the closest I can come to your attempted command is:

1. read the list into a shell array

   mapfile -t files < list.txt
   

2. use the bash shell's printf to construct the predicate list

   printf -- '-name "%s" -o ' "${files[@]}"
   

3. use eval to evaluate the resulting command string

There's a wrinkle here inasmuch as if we use printf's format re-use feature to construct the list in this way, we're left with a 'dangling' -o; we can work around this by terminating the list with a -false test (since -o -false is a Boolean no-op) so that our final predicate string becomes

"\( $(printf -- '-name "%s" -o ' "${files[@]}") -false \)"

Putting it all together - given

$ tree dir
dir
├── Folder_1
│   ├── file1.txt
│   ├── file2.txt
│   ├── file3.txt
│   └── file4.txt
├── Folder_2
│   ├── file5.txt
│   ├── file6.txt
│   └── file7.txt
└── Folder_3
    ├── file8.txt
    └── file9.txt

3 directories, 9 files

and

$ cat list.txt
file2.txt
file5.txt
file9.txt

then

$ mapfile -t files < list.txt

$ eval find dir/ "\( $(printf -- '-name "%s" -o ' "${files[@]}") -false \)" -print
dir/Folder_1/file2.txt
dir/Folder_2/file5.txt
dir/Folder_3/file9.txt

To copy files instead of just listing them, you could then do

$ mkdir newdir
$ eval find dir/ "\( $(printf -- '-name "%s" -o ' "${files[@]}") -false \)" -exec cp -t newdir/ -- {} +

resulting in

$ tree newdir
newdir
├── file2.txt
├── file5.txt
└── file9.txt

0 directories, 3 files

Note: the eval command is powerful and potentially open to abuse: use with care.

In practice, given that you appear to want to find only a small number of files, the KISS approach would be to accept the performance hit of multiple find calls and just use a loop:

while read -r f; do
  find dir/ -name "$f" -exec cp -v -- {} newdir/ \;
done < list.txt

or even using xargs

xargs -a list.txt -n1 -I@ find dir/ -name @ -exec cp -v -- {} newdir/ \;

I would just use grep and sort -u:

$ grep -Po '/elv/\K[^/]+' NASA_access_log_Aug95.txt | sort -u
ATLAS_CENTAUR
DELTA
TITAN

The -P enables Perl Compatible Regular Expressions which let us use \K which means "ignore anything matched up to this point". The -o means "only show the matching portion of the line". Then, the regular expression means "look for /elv/, ignore everything matched until the /elv/, and then look for one or more non-/ characters ([^/]+).