bash

An example of how to use jq.

Use #! in a shell script to select the program to run instead of the shell.

This is a nice command to get a list of commits with messages for each in a list: git log --pretty=oneline --abbrev-commit git log --pretty=format:"%cd %h %s"

According to http://vimregex.com, the {-} construct will do a non-greedy match. I've been searching for this for a long time. For instance, let's say I have used inline quotes for a Markdown doc and I want to change them to bold using

if [[ "$1" =~ s.* ]] then echo small elif [[ "$1" =~ l.* ]] then echo large else echo small or large fi See: Bash V3.2 Reference Manual

Often times it's necessary to watch progress of things like copying a file or checking if a process is still running. This is a job for the Linux "watch" command.

Often times it is necessary to do things that need to be cleaned up when a shell script exits, remove temporary files for instance. Cleanup should occur when the script exits normally or when it is interrupted. Interruptions can be a BREAK (usually ^C)

If you build a lot of systems and use SSH you'll undoubtedly run into this problem a lot: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It

The cut command is very useful for picking things like finding the PID of a process to kill. However, the default delimiter is TAB, making the cut command rather difficult to use. The solution is to squeeze the redundant spaces into a single space

This sets up your account to save any file converted from CRLF to LF with LF instead of converting them to CRLF. This is necessary for running shell scripts on Cygwin. $ git config --global core.autocrlf input $ git config --global -l core.autocrlf=input

This Stack Overflow article covers the subject well: http://stackoverflow.com/questions/4561895/how-to-recursively-find-the-latest-modified-file-in-a-directory This is a slightly modified example: $ find . -type f -printf "%T@ %p\n" | sort -n | cut -f2- -d" " | tail -7 ./dir_a/README.md ./dir_a/hello.java ./dir_b/

I use SSH and SCP commands in the shell and in scripts, a lot. Entering a password every time gets tiresome. Fortunately SSH can authenticate automatically if you store the private key of the remote system on your computer. I've been using this "

Do you use Vim in a black background Linux shell? Chances are you'll find the default colors for Vim or ls are hard to read, especially blue on black. Tell Vim You are using a Dark Background Configuring Vim is done by adding commands

How do you list the contents of a tar file in a tar file? Until recently, I had to untar the file then use tar tf to list the contents of the embedded tar file. To my surprise I found that Vim can actually

I use Linux in Virtual Machines all the time. Most of the time I setup the VM with a bridged network adapter and SSH. This allows the VM to access the Internet and allows logging into the shell remotely using SSH. Sometimes it's not

Cygwin has all of the Linux goodies, making Windows a tolerable development platform. It provides the standard OpenSSH packages. Install Cygwin. Install openssh clients and servers package. Run ssh-host-config. Skip the install as a service thing, instead just enter: $ /usr/sbin/sshd in the

This is easiest done using /etc/ssh_config or .ssh/config. The format of the file is: Host SSHConfigKeyword parameters... You can list specific host names or use * to apply configuration to all hosts you plan to connect to. The file below will forward

Here's a simple example: #!/bin/bash # http://www.tutorialspoint.com/unix_commands/getopt.htm usage() { echo usage: $0 -- --ge0IP 10.132.56.250 --ge1IP 192.168.99.1 exit 1 } # read the options TEMP=`getopt --long ge0IP:,ge1IP: -- "$@"` eval set -- "$TEMP"

Here's an example: #!/bin/bash IP=192.168.11.1 function split() { export IPARRAY IFS='.' read -ra IPARRAY Output: process 192 process 168 process 11 process 1 192 168 11 1 192

DOS File Format Error If you use Cygwin to write shell scripts on Windows, chances are you'll accidentally create a shell script in DOS format. When this happens Bash will flag a syntax error in the script. Usually it looks like a string has

Gdrive 2 Sometimes uploading or downloading files via a web page is a pain. With 15 GB of free storage, Google Drive is a great resource. Google had an unsupported tool to use from the command line, but it's not available anymore. The tool