bash.md

Bash

Explanation of the tool and it's purpose. Be Brief and say it concisely in a sentence

Key Terms

Environment variables

global: Env var set upon initialization of a shell and can be used across all shells. To make it global export variable to ~/.profile

❯ cat .zprofile

# Setting PATH for Python 3.9
# The original version is saved in .zprofile.pysave
PATH="/Library/Frameworks/Python.framework/Versions/3.9/bin:${PATH}"
export PATH

local: Env var that is set during a shell session and is erased when the shell is closed.

export MY_VARIABLE="some value"
echo $MY_VARIABLE # some value

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Shell variables

Variables created in a script and only accessible by the script

MY_SHELL_VARIABLE="some value"

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Common Commands

Run the following command only if the first command succeeds

&&
echo Hello && echo World

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Run the following command output into the next command

|
cat /etc/passwd | grep --color -E "^[a-z]{3}:"

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Text transformation tool for simple transformation like fined/replace

sed [options] <pattern_to_replace> <new_pattern_to_add> <file_with_contents>
-i '<.extension>' back up file to be made before changes
-e'<pattern to follow>' substitute command to run on file
s/<pattern_to_replace>/<pattern_to_insert>/g s(substitute) /(separates the command and pattern) g(perform replacement globally)
example: sed -i '' -e 's/,/ /g' apple.csv

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Formatting tool for text or formatting transformation

awk [options] BEGIN { <action_before_processing> }; <optional_condition> { <action_after_processing_line>}
-F Field separator for the input file
BEGIN { print "<PRINT_THIS_STUFF\tAND_THIS_AFTER_TAB>" } Execute contents before processing any lines
NR > <line_num> If condition (current record number is greater than digit) is full filled execute the following action
{ print $<field_number> "\t" $<field_number> "\t" $<field_number> } Main action block of that is executed for each record line in input file
example: awk -F " " ' BEGIN { print "Date\t\tPrice\t\tVolume" }; NR > 1 { print $1 "\t" $2 "\t" $7 } ' apple.csv
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Uncompress a .zip file

unzip <path to zip file> -d <location to save decompressed file>
-d show all containers

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Tail display last few lines of a file

tail -f /path/to/file
-f follow bottom of file if any changes are appended

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See all environment variables both local and global

env

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Find patterns or words in one or more files. Search tool

grep [options] "<text_to_search_for>" <file_to_search_in> -i case insensitive
-E extended regular expressions
--color highlight the matching text in color

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ADVANCED COMMANDS

COMMAND

``
-

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COMMAND

``
-

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Configs

Name_of_config

What does the config do
Config example and definition of each term

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Processes

Process

1. steps
2. step
3. step

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Links

Bash Crash Course