Append a string to another with Regex tools

Question

For the life of me, I cannot find out how to do this very simple procedure. I want to:

read a file, which consists only of number on each line
append characters before and after the number in the file.

For example, in the contents of the file:

1
2
3

would turn into:

file1.txt
file2.txt
file3.txt

I've tried this:

sed 's/[0-9]+/{file&.txt}/' file_name.txt

but nothing happened. I see snippets online that say use {0} or {/1} but I am having a hard time finding an explanation of what this means.

The end goal of this is to have xargs copy all the filenames in this text to another directory. I am sure there is probably another way to accomplish this without the text file I am doing here. If anyone has a simpler answer to that end goal, that would be nice to hear, although I also want to figure out how to use sed! Thanks.

captcha · Accepted Answer · 2013-07-01 22:34:13Z

6

Yes, this does work:

$cat file
1
2
3
$sed 's/.*/File&.txt/' file
File1.txt
File2.txt
File3.txt

answered Jul 1, 2013 at 22:34

captcha

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Comments

Lorkenpeist · Accepted Answer · 2013-07-01 22:30:31Z

3

In sed, + is not a special character, and literally means the + character. You need to escape it with backslash:

sed 's/[0-9]\+/file&.txt/' file_name.txt

Alternatively you can use the -r option, which adds several special characters (including +):

sed -r 's/[0-9]+/file&.txt/' file_name.txt

answered Jul 1, 2013 at 22:30

Lorkenpeist

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2 Comments

potong Over a year ago

The -r switch in GNU sed adds nothing more than "syntactic sugar" in that it removes the need to prepend a backslash before the metacharacters ()+?|

newt Over a year ago

Thanks; I chose this answer b/c it more directly addressed the question.

doubleDown · Accepted Answer · 2013-07-03 07:51:56Z

1

Not sure why you need sed for your end goal (or xargs for that matter). You can simply do:

while read -r name; do 
    cp "File${name}.txt" /path/to/copy
done < file_name.txt

edited Jul 3, 2013 at 7:51

doubleDown

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answered Jul 2, 2013 at 5:10

jaypal singh

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