Useful Bash Commands

login     # prompts for username and then password to log in
man       # man (command) returns documentation a command

Directory Commands

pwd       # print working directory
cd        # changes directory to home
cd \      # changes directory to (/path)
cd ..     # moves up one folder in the directory
ls -al    # lists contencts of directory, -a includes hidden items, -l includes details

File Operations

mkdir    # make a new directory
touch    # create a file
open     # open a file
mv       # move (file) (to), can also be used to rename a file
cp       # copy (file) (to) 
rm       # delete a file

Other Utilities

echo    # print commands screen
date    # print date
cal     # print calendar (year)

Setup

# create user name and email for tagging contributions later
git config --global user.name "USERNAME"   
git config --global user.email "EMAIL" 

Connecting to Git can be done through a username/password or through SSH verification.

Username/Password

This didn’t work for ubdates scheduled through crontab.

SSH

First, check for SSH keys with;

cd ~/.ssh  # navigate to user/.ssh folder
ls -a      # list all files

A public SSH key is in id_rsa.pub, which can be opened in a text editor.

If no id_rsa file exists, or if you wish to create a new SSH key, you can use the following command to generate a new SSH key;

ssh-keygen -t rsa -b 4096 -C "your_email@example.com" # run this if id_rsa file does not exist

This will prompt you for the file location where the SSH key should be saved – id_rsa is the default file.

From here, follow the steps to add an SSH key, summarized below.

First, create a config file for the SSH agent with;

touch ~/.ssh/config

Open the config file in a text editor and add the the following commands;

Host *
 AddKeysToAgent yes
 UseKeychain yes
 IdentityFile ~/.ssh/id_rsa

Next, from Terminal, add the key from the file (e.g. id_rsa) to the ssh agent with;

ssh-add -K ~/.ssh/id_rsa

Finally, add the ssh key to the GitHub account.

And test the connection with;

ssh -T git@github.com

Working From a Repository

Create a repository through GitHub’s user interface (log in and select ‘new repository’).

Then create a directory on a local computer, possibly using bash commands; mkdir and cd.

The simplest way is to clone the repo from GitHub with;

git clone (url)     # this will clone from the url to the current directory

Another way, from inside the directory that is to be the local repo, issue these commands;

git init   # initialize a repo
git remote add origin (url or SSH address) # point local repo to remote repo

Switching between SSH and HTTPS Access

In both examples below, replace ‘USERNAME/REPOSITORY’ with the appropriate values. From within the local repo folder,

Change from HTTPS to SSH with;

git remote set-url origin git@github.com:USERNAME/REPOSITORY.git
git remote -v # list fetch and push destinations, should start with git@github.com

Change from SSH to HTTPS with;

git remote set-url origin https://github.com/USERNAME/REPOSITORY.git
git remote -v # list fetch and push destinations, should start with https://github.com/

More detailed guide here.

Other methods for addressing ‘Device not configured’ errors here.

Repository Maintanence And Collaboration

Git workflow

Useful commands;

git pull    # adds files from the configured remote repo to your local repo and workspace
git add .   # adds all new files to be tracked
git add -u  # updates all files
git add -A  # does both '.' and '-u'
git commit -m "message" # saves changes local repo
git push    # updates repo on GitHub

Collaborators can all access the GitHub repo through push/pull commands. In collaborative settings you might need to pull, so that your repository is current, before pushing changes from the local repository to the remote repository on GitHub.

gitup: combines add, commit, and push into one command

alias gitup="git add -A; git commit -m 'auto'; git push"

gitupall: updates all git repos in my git folder

function gitupall{
for filename in /Users/mac/git/*; do
echo "**************************updating $filename"
cd "$filename"; 
gitup
cd ..
done
}

schedule: schedules a command to be executed periodically

function schedule(){
crontab -l | { cat; echo "$1"; } | crontab -
}

# format for string argument for crontab;
* * * * * "command to be executed"
- - - - -
| | | | |
| | | | ----- Day of week (0 - 7) (Sunday=0 or 7)
| | | ------- Month (1 - 12)
| | --------- Day of month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)

Example use;

# e.g. use: schedule updating of all repos each hour
schedule "0 0-23 * * * gitupall"
crontab -l # lists crontab jobs after schedule call

Bash Aliases, Functions, Scheduled Commands

In my root directory, I have a file called .custom_commands with contents;

# aliases

# goes to my folder of git projects
alias gitgo="cd /Users/mac/git; ls"
echo 'sourced alias gitgo'

# pushes updates on a git project
alias gitup="git add -A; git commit -m 'auto'; git push"
echo 'sourced alias gitup'

# functions

# schedule "(m h DoM M DoW command)"
# schedules command to be executed at 
# minute m of hour h on DoM days of the month in months M or DoW days of the week.
function schedule(){
crontab -l | { cat; echo "$1"; } | crontab -
}
echo 'sourced function schedule'

# for updating all git projects, schedule this to be done periodically
function gitupall(){
for filename in /Users/mac/git/*; do
echo "************************** updating $filename"
cd "$filename";
git remote -v    # prints the fetch and push destinations
gitup
done
cd # return to home directory
}
echo 'sourced function gitupall'

I also have a .bashrc file in my root directory, which sources the custom commands. Particularly the contents of the .bashrc file are;

# Source system-wide definitions
if [ -f /etc/bashrc ]; then
    . /etc/bashrc
fi

# source file with function definitions
source ~/.custom_commands

I also have a file in my root directory for scheduling, called .scheduled with contents;

# put all scheduled functions here

# source custom commands
source ~/.custom_commands

# activate key agent
eval "$(ssh-agent -s)"

# test SSH key / print username
ssh -T git@github.com

# update all git repos
gitupall

I then scheduled this file to be read hourly by opening a terminal session, which sources .bashrc at initialization thereby sourcing my custom commands, and running;

schedule "0 0-23 * * * source ~/.scheduled"
crontab -l # the scheduled job should be listed as a crontab job