[Unix] Unix tools

README.md

File

Print from start_lineno - end_lineno

sed -n start_lineno,end_linenop file Ex: sed -n 5,10p file

Run in parallel

To run 10 processes in parallel xargs -P10
Ex: Run git pull on all folders in current directory:
ls | xargs -P10 -I{} git -C {} pull

BASH.md

1. To quickly jump to important folders in your terminal, bookmark them as
   ln -s path/to/project ~/.bookmarks/@project
   then to navigate to project folder - goto @project

   But before you can do that do below -

   1. create directory ~/.bookmarks
   2. Add below to .bashrc

   if [ -d "$HOME/.bookmarks" ]; then
       export CDPATH=".:$HOME/.bookmarks:/"
       alias goto="cd -P"
       _goto()
       {
   	    local IFS=$'\n'
   	    COMPREPLY=( $( compgen -W "$(/bin/ls ~/.bookmarks)" -- ${COMP_WORDS[COMP_CWORD]}))
       } && complete -F _goto goto
   fi
   

2. To run a script that has dependencies on other scripts from any location, add - script_dir="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )" command gets the script's source file pathname, strips it to just the path portion, cds to that path, then uses pwd to return the (effectively) full path of the script. This is assigned to script_dir. After all of that, the context is unwound so you end up back in the directory you started at but with an environment variable script_dir containing the script's path. Now script_dir can be used as follows - source "${script_dir}/informal_module.sh" (Here informal_module.sh is assumed to be in same dir as current script) More here - https://advancedweb.hu/unit-testing-bash-scripts/ and https://stackoverflow.com/questions/39340169/dir-cd-dirname-bash-source0-pwd-how-does-that-work

3. Use Bash Strict Mode

#!/bin/bash
set -euo pipefail
IFS=$'\n\t'

Adding above to your scripts causes bash to behave in a way that makes following classes of subtle bugs impossible -

• immediately exit if any command has a non-zero exit status
• a reference to any variable you haven't previously defined is an error
• errors in a pipeline from being masked.