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Table of Contents
task boiler
Place to cook the tasks. Once they are boiled enough, move them to a separate plate.
Start the first heading with “=====”
apply unix commands to all but the first line
Situation
Let's say we want to sort a series of numbers in descending order but keep the header at the top. For example, given
$ echo -e "value\n8\n2\n6\n3" value 8 2 6 3
we want to output
value 2 3 6 8
We can't directly use 'sort' since it will sort the header as well.
$ echo -e "value\n8\n2\n6\n3" | sort 2 3 6 8 value
Bare bones solution
Create a script called 'body' with the following contents
#!/usr/bin/env bash # # body: apply expression to all but the first line. # Use multiple times in case the header spans more than one line. # # Example usage: # $ echo -e "value\n8\n2\n6\n3" | body sort # IFS= read -r header printf '%s\n' "$header" "$@"
Make it executable
chmod +x body
place it somewhere in your PATH (say ~/bin)
mv body ~/bin
This script will apply any unix command to all but the first line. For example, using it on our example
$ echo -e "value\n8\n2\n6\n3" | body sort value 2 3 6 8
Practical solution
I got the above script from https://github.com/jeroenjanssens/dsutils/blob/master/body . The underlying repository (https://github.com/jeroenjanssens/dsutils) contains many such useful scripts (ex:- header - to add, replace, and delete header lines). A more practical approach is to clone the entire repository and add the repo location to your PATH.
I did it as follows.
Remove the bare bones script we added in the previous step
% rm ~/bin/body
Clone the repository
% mkdir -p ~/github/jeroenjanssens % cd ~/github/jeroenjanssens % git clone git@github.com:jeroenjanssens/dsutils.git Cloning into 'dsutils'... remote: Enumerating objects: 62, done. remote: Counting objects: 100% (62/62), done. remote: Compressing objects: 100% (52/52), done. remote: Total 62 (delta 20), reused 48 (delta 10), pack-reused 0 Receiving objects: 100% (62/62), 18.59 KiB | 9.29 MiB/s, done. Resolving deltas: 100% (20/20), done.
Update the PATH in ~/.bashrc by adding the following lines
#------------------------------------------------------------------------------ # Add data science utils such as body, header export PATH=~/github/jeroenjanssens/dsutils:$PATH #------------------------------------------------------------------------------
Open a new bash session and verify that these utilities are correctly picked up.
% which body /home/rajulocal/github/jeroenjanssens/dsutils/body % which header /home/rajulocal/github/jeroenjanssens/dsutils/header
Verify that the utilities are working as expected.
% echo -e "value\n8\n2\n6\n3" | body sort value 2 3 6 8
Works with any command
The beauty of this approach is that you can use it with any unix command (and not just sort). For example, you can grep a value and it will show the header along with the value.
% echo -e "value\n8\n2\n6\n3" | body grep 8 value 8
How I came across it
I came across it while reading the book “Data Science at the Command Line” (2nd Edition) by Jeroen Janssens (https://smile.amazon.com/Data-Science-Command-Line-Explore/dp/1492087912). The book is available for free at https://datascienceatthecommandline.com/2e/ . The 'body' and 'header' commands are discussed in https://datascienceatthecommandline.com/2e/chapter-5-scrubbing-data.html#bodies-and-headers-and-columns-oh-my .