CLI - Xensoft

Use sed to Insert Text Every 'n' Lines/Characters

There are a lot of overly complicated ways to insert a line after every nth line, but the simplest way I find is the following: sed '0~3 s/$/\nMy Text/g' < input.file In a file with six lines you get something like the following: Line 1 Line

CLI

Check out a _link from OBS

If you're looking to edit the _link file stored in the repository underlying your OBS you can check it out with the --unexpand-link option. Otherwise you'll end up with the _service file: osc checkout --unexpand-link <Project> <Package> # or if you're already in the project's directory: osc

CLI

Always Display Filename with grep

The easiest way to accomplish this is if you have a relatively recent GNU version of grep. Then the -H version is available to you: printf "This\nis\a\ntest" > /tmp/grep.test grep -H 'is' /tmp/grep.test /tmp/grep.test:This /tmp/grep.test:is

SSH

Add/Remove Passphrase from Existing Private Key

If you've got a private key you're fond of that either has or lacks a passphrase(password) and you'd like to add (because you'd like to put it someplace you trust slightly less) or remove (because you're moving it someplace you trust more [really?]) it's really straight forward. To add

CLI

Best Way to Copy Dotfiles

I've seen a lot of convoluted solutions floating around regarding how to copy files starting with .. The problem everyone is trying to avoid is that when you run something like: cp -r A/.* B/ The above command starts copying everything the entire "A" directory (.) and then from the

CLI

Become an SSH Ninja: SSH Tips and Tricks

OpenSSH has some pretty cool tricks up its sleeve beyond it's "Clark Kent"-esque ability to provide a secure command line interface on a remote system. Here are some of its more "Superman"-type abilities: Public-Key Authentication Learn to Love Your .ssh/config Agent Forwarding Sharing

CLI

Redirect Output of an Already Running Process

Have you ever started a long running command and then wanted to put it in the background but it's sending its output to STDOUT? Here's a script that uses gdb to swap a processes file descriptors so you can send all that output to a file, or /dev/null after

CLI

Use Redirection Instead of Temp Files

There are certain commands that really want to read input in from a file, like diff. However, if what you're trying to manipulate or use with one of these commands is actually output from another command usually you'd have to write this information out to a file before reading it

CLI

Adding a Little Color to Recursive diffs

I have routine need to recursively diff two large directory trees with small changes sprinkled throughout. After staring at pages and pages of one diffed file after another it becomes easy to lose track of what two files' differences I'm looking at. An easy way to keep track of things

CLI

Simple CLI Based Timer Alias

Here's a quick alias that will start up a timer and report the total time after a control-C. alias timer='which banner>/dev/null 2>&1;[ $? -eq 0 ]&&c=banner||c=echo;export ts=$(date +%s);p='\''$(date -u -d @"$(($(date +%s)

OSX

Speed Up Terminal Tab/Window Load Time on OSX

Terminal uses /usr/bin/login to launch new shells, by default this prints out the last login time and the contents of /etc/motd. To look up the last login time login searches through the ASL (Apple System Log) database in /var/log/asl/. These log files can be very

CLI

Setup a Remote Shell over ICMP (ping)

There may be a tighter way to accomplish this, but these are the basic steps for setting up a remote shell over ICMP. remote First, on the remote system we setup some named pipes, and attach them to the STDIN and STDOUT (we also direct STDERR to STDIN) of a

OSX

Switching from MacPorts to Homebrew

Decided I'd give Homebrew a try - here's the process I used to switch over. Make a list of your ports for reference later: port installed > ports.txt Might be worth going through that list, clear out the dependency ports you can identify and leave a list of the

CLI

Find IPs Accessing your Site Most

List IPs that have made requests to an Apache server in ascending order based on the number of requests. { cat /var/log/httpd/access.log!(*.gz) & gzip -dc /var/log/httpd/access.log.*.gz; } \ | cut -d ' ' -f 1 | sort | uniq -c | sort -n 337 8.29.198.

CLI

Sort Human Readable File/Directory Sizes

When using sort the -h or the longopt version --human-numeric-sort sort human readable numbers (e.g., 2K 1G) du -hd1 | sort -h 321M ./.ccache 508M ./build-perl-squeeze 862M ./7.6.1 Add -r to sort to get the largest listed first.

CLI

A Couple Ways to Return a Random Number on the Command Line

Lets explore a couple ways to get random numbers on the command line. Anyone who attempts to generate random numbers by deterministic means is, of course, living in a state of sin. John von Neumann $RANDOM Bash Internal $RANDOM is an internal Bash function (not a constant) that returns a

CLI

Re-call Command Line Arguments in BASH

BASH's history expansion character, ! has many features, including !: for choosing a specific argument (or range of arguments) from the history. The gist is any number after !: is the number of the argument you want, with !:1 being the first argument and !:0 being the command. echo one two three one

CLI

Simple Way to Get your External IP on the Command Line

This is an easy way to see what IP a website is seeing you come from: curl httpbin.org/ip { "origin": "52.11.93.181" } curl icanhazip.com 52.11.93.181 Lots of other options, but these are some of the shortest I've seen.

CLI

Google text-to-speech in MP3 Format via the Command Line

The function will take a string and create an MP3 of the string being spoken and named after the first 15 characters of the string: t2s() { wget -q -U Mozilla -O $(tr ' ' _ <<< "$1"| cut -b 1-15).mp3 "http://translate.google.com/translate_

CLI

A Couple Ways to Identify the Shell you're Using

ps -p $$ PID TTY TIME CMD 76146 ttys002 0:54.05 -bash echo $SHELL /bin/bash The first gets the PID and command of the current shell, the second is an environment variable that should be set in most shells.

CLI

List DEBs by Size

dpkg-query -Wf '${Installed-Size}\t${Package}\n' | sort -n Similar the the RPM equivalent. However, the above doesn't seem to always list the "Installed Size" - you can always fall back to this brute force method: dpkg --get-selections | cut -f1 | while read pkg; do dpkg -L $pkg | xargs

CLI

Use Multiple CPU Cores(Parallelize) with Single Threaded Linux Commands

Note: If things are not working as described below check the version information for parallel. parallel --version WARNING: YOU ARE USING --tollef. IF THINGS ARE ACTING WEIRD USE --gnu. ... Either add --gnu to all your parallel commands, or edit /etc/parallel/config and make sure it lists --gnu and not

CLI

Unpacking or Repacking initrd.img or initramfs.img

Need to tinker with an initrd.img or initramfs.img? Here are the steps to unpack these files and then put them back together again if you've made any changes. First step, make a copy of the initrd.img or initramfs.img in question: cp /boot/initramfs-*.img /tmp The

CLI

How a BASH Script Can Find Its Own Location

Most foolproof method I'm aware of is the following: SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd && echo x)" SCRIPTDIR="${SCRIPTDIR%x}" or if you're not worried about newlines at the end of your directory names: SCRIPTDIR="$( cd

CLI

Exploring the BASH_SOURCE Array

$BASH_SOURCE is the call stack of scripts with the top of the stack being the currently executing sourced script, sourcing another script from the current one will push it on top of the stack. To get an idea of how this works you can set up a directory tree