anew(er)

Append lines from stdin to a file, but only if they don't already appear in the file. Outputs new lines to stdout too, making it a bit like a tee -a that removes duplicates.

Installation

To install the binary, clone the git repository and build the golang binary locally.

git clone https://github.com/SecGus/anewer.git
cd anewer
go build anewer.go
sudo mv ./anewer /usr/bin/

Usage Example

Here, the files called things.txt and things2.txt contain lists of numbers. newthings.txt contains a second list of numbers, some of which appear in things*.txt and some of which do not. anewer is used to append the latter to the last file specified as a parameter (or the value set in the -o argument.

▶ cat things.txt
Zero
One
Two

▶ cat things2.txt
Zero
Six
Three

▶ cat newthings.txt
One
Two
Three
Four

▶ cat newthings.txt | anewer -o added-lines things.txt things2.txt
Four

▶ cat added-lines
Four

▶ cat newthings.txt | anewer things.txt things2.txt
Four

▶ cat things2.txt
Zero
Six
Three
Four

Note that the new lines added to things2.txt are also sent to stdout, this allows for them to be redirected to another file or command:

▶ cat newthings.txt | anewer things.txt things2.txt | echo $(xargs)
Four

Flags

• To view the output in stdout, but not append to the file, use the dry-run option -d.
• To append to the file, but not print anything to stdout, use quiet mode -q.
• To trim trailing whitespaces before making the comparison, use -t.
• To define a file to append the output to, without needing to specify it as a check value, use -o.