These tricks have saved me a lot of time. Many of them I started using after reading this Definitive Guide to Bash Command Line History by fellow Hacker News reader, pkrumins. It includes a much deeper look at history than the quick examples I cover here. 

Search Your History Quickly

No more history | grep ... or hitting the up button 20 times. Just open a command prompt, press Ctrl-R, and begin typing a word in your command. As you type, the most recent command matching what you type will appear. To continue searching backwards in the history, hit Ctrl-R again. Then hit the left or right key to edit the command or hit enter to run it. 

Increase Your History Size

Once you know how to search your history, make sure your commands stick around for a while. By default, the history size is pretty low, usually only 500. To increase your history size, add the following to either ~/.bashrc, ~/.bash_profile, or /etc/profile:

export HISTFILESIZE=1000000000
export HISTSIZE=1000000

Analyze Your History

Once you've built up a sizable history, analyze it to determine possible aliases that will reduce typing time. To see the top 30 most used commands, run:

cut -f1 -d" " .bash_history | sort | uniq -c | sort -nr | head -n 30

To see the top 30 most used commands including arguments, run:

sort .bash_history | uniq -c | sort -nr | head -n 30

Stop Getting Annoyed When You Forget sudo

I used to get so mad when I forgot to sudo a command, especially a long one. Not any more. To repeat a command using sudo, run:

sudo !!

Reuse Arguments

Say you want to backup a file then edit that file. Here's how you can reuse an argument from the most recent command:

cp a-very-long-file-name.txt a-very-long-file-name.txt.bak
vi !^

Also, you can use !!:N for the Nth argument, !!:N-M for the Nth to Mth arguments,  !!:$ for the last argument, or !!:* for all arguments.

Self Promotion

If you're a software engineer with Linux experience in NYC, consider coming to Hirelite: Speed Dating for the Hiring Process tomorrow evening (4/27).

I realized I made my first Delicious bookmark just over four years ago. Here's a visualization of my links. It's a decent approximation of what I know.

Update: I switched to pinboard.in after all the Delicious shutdown controversy.

Who knew threads and romantic relationships had so much in common? For those of you new to threads, threads (and processes) allow computers to seemingly do multiple things at once, where each thing is a separate "thread" of execution. On a computer with a single processor, the processor spends short amounts of time executing each thread before switching to another thread to execute. On a multiprocessor system, processors execute threads simultaneously, switching between threads when there are more threads than processors.

For those of you new to romantic relationships, I don't have much advice for you other than: Don't tell your significant other that you're treating your relationship as a series of thread synchronization problems!

Also, I'm probably perpetuating some stereotypes here. Sorry, it just makes the examples easier.

Thread Synchronization Issues

Deadlock occurs when threads cannot proceed because they're waiting on each other.

Romantic relationship example: You and wife have to wake up at 6am to catch a flight. You half-wake-up at some point in the morning and think, "she'll wake me up," and go back to sleep. The problem is, now it's noon, and you've both been thinking the same thing for six hours. You missed your flight due to relationship deadlock.

Livelock occurs when threads cannot proceed because they're too busy responding to each other.

Romantic relationship example: When was the last time you heard an obnoxious couple talking on the phone? Think back to the end of their phone conversation. It probably ended like this.

1: Love you. Talk to you later.
2: Love you too. Bye.
... both wait ...
1: You hang up first.
2: No you hang up first.
1: No you...

You're witnessing relationship livelock. Neither person in the couple nor the couple as a whole can proceed because they're too busy responding to each other.

Starvation occurs when one thread is deprived of resources by greedy or mis-prioritized threads.

Romantic relationship example: You and your boyfriend share a checking account and deposit money into it on the first of the month. You routinely make small purchases every day. Your boyfriend rarely makes purchase, but when he does, he buys something big. After the first of the month, you successfully make your small purchases for a few days, but then your boyfriend buys an iPad. All your attempted purchases are now denied. You're suffering from starvation.

Race conditions occur when success depends on the order in which threads run.

Romantic relationship example: Your son wants to go bungee jumping with his friends. He knows that each parent requires that he ask both parents for permission. Using a clever turn of phrase, he realizes that he can exploit a relationship race condition to get what he wants by asking the stricter parent first.

Son (approaches strict mother): Can I go bungee jumping?
Mother: No, but ask your father.
Son (approaches lenient father): Can I go bungee jumping?
Father: Yes, but ask your mother.
Son: I already did.
Father: Great. Hope you have fun!

Thrashing occurs when threads make little or no progress due to the overhead of context switching.

Romantic relationship example: A couple tries to decide whether or not to get a pet. The argument gets heated. They keep bringing up unrelated topics. Each time a new topic comes up, they spend five minutes on it.

1: Having a dog would be so much fun!
2: You would never clean up after it.
1: What?! I clean all the time.
... five minutes later ...
1: Well at least I don't leave clothes all over the place.
2: Psh. I'm the only one that ever does the laundry. I can leave my clothes wherever I want.
... five minutes later ...
2: I don't know if I can talk about this anymore. I'm just going to go watch TV to cool down.
1: You watch TV all the time! We don't even need a pet. You spend all your time with the TV.

Every context switch gets the couple further away from where they started and from the problem they're trying to resolve. They're thrashing.

Busy waiting occurs when one thread continuously checks if it may proceed, robbing other threads of processing time.

Romantic relationship example: A couple is getting dressed for a party. The man is dressed and ready to go. The woman is nowhere near done. The man keeps interrupting the woman to ask her if she's ready yet. The man is busy waiting.

Self Promotion

If you're a developer and you like these sorts of problems, consider attending Hirelite: Speed Dating for the Hiring Process on Tuesday, April 27th in NYC where companies will be looking for great software people.

Since starting Hirelite, where we get companies and software people talking directly, I've heard a lot of horror stories about working with recruiting agencies. When I hear these stories, I can't help but think of black hat vs. white hat hacking and SEO, so I call recruiters who engage in unethical practices "black hat recruiters". Black hat recruiters resort to the tactics below because they're too lazy to confront the real challenges involved in finding and matching good people and good companies. Please note that not all recruiters are bad, and some provide a lot of value, but this post is not about those recruiters. This post is about black hat recruiting where tactics range from lies to ethically gray practices to illegal activity (in approximate order of how common they are):

Posting misleading job descriptions - This is by far the most common form of abuse. Recruiters will post a job description for a legitimate position for a client, but falsify some of the information to entice candidates. For example, a recruiter will inflate the salary/compensation portion of the job description or inflate the job responsibilities while dumbing down the job requirements.

Posting bait-and-switch job descriptions - Black hat recruiters will advertise a job that does not exist or is already filled just to receive resumes from job seekers that they can contact about other job opportunities. This is very similar to a tactic that black hat apartment brokers use (mentioned in Rent Hop's comparison of headhunters and apartment brokers).

Surreptitiously modifying a job seeker's resume - Black hat recruiters often request a resume in a format they can modify. They will make modifications to job seekers resumes without telling job seekers and then give the modified resume to their clients. Modifications range from obscuring contact information so that the recruiter is always in the loop to more liberal modifications like inflating experience and skills. Nothing's worse than getting to an interview and finding out that you know COBOL from the hiring manager reading it off your resume.

Approaching other companies job seekers interview with - Recruiters often ask job seekers what other companies they are interviewing with under the guise of tailoring their search to the job seeker. Some recruiters will go as far as to ask who specifically the job seeker is in contact with. Armed with that information, a recruiter will contact the other companies and try to send competing job seekers. I've spoken to one job seeker who suspected this was happening and caught their recruiter in the act. This job seeker told the recruiter a friend's name and had the friend wait for the recruiter's call. The friend didn't have to wait long. Only 10 minutes after the initial call ended, the recruiter called the job seeker's friend. The recruiter denied everything.

Cold calling and pressuring low level employees - Black hat recruiters will call low level employees at a company and threaten termination and legal repercussions unless the employee passes the recruiter along to a hiring manager at the company.

Buying resumes from hiring companies - Black hat recruiters will give discounts to companies that will pass all the resumes for a particular position along to the recruiter. These resumes could be from other recruiters or from candidates who contacted a company directly.

Pressuring job seekers into interviews - Black hat recruiters will pressure job seekers into interviews that they don't want to go on. Sure, job seekers should stand up to them and say, "I don't want that job," but when a recruiter responds, "I'm not going to put you in front of <company> unless you go to this interview," job seekers may give in.

Promising exclusivity to job seekers - Black hat recruiters will promise a job seeker that they will not submit other job seekers for the same position as long as the job seeker agrees not to talk to any other recruiters. The recruiter then submits multiple competing job seekers for a position. If one is rejected, he tells that job seeker that the company decided there wasn't a fit and continues to send him to other companies.

Recruiting the references of a job seeker - Black hat recruiters request references from job seekers and recruit those references. Later, job seekers hear from their references that their recruiter pressured them for resumes to send to clients, sometimes for the exact job the original job seeker was up for!

Faking a relationship - Black hat recruiters will hear that Dunder Mifflin, a company they have no relationship with, is hiring. Instead of approaching Dunder Mifflin about working for them, the recruiter will solicit resumes from potential job seekers for exciting new openings at Dunder Mifflin. The recruiter will then approach Dunder Mifflin with the resumes they have. If Dunder Mifflin rejects the recruiter, the recruiter will tell the job seekers that Dunder Mifflin said there wasn't a fit for them.

Discrediting an employee's current company - Black hat recruiters will contact an employed potential candidate and tell them that their current company is in a precarious financial state and offer to find the employee another job. Black hat recruiters will even do this to employees of their own clients.

Simulating expiring offers - When a company sends an offer to a job seeker, black hat recruiters will tell the job seeker that they only have X days (where X is usually 1 or 2) to accept the offer; otherwise, it will be rescinded. This practice is a bit more rare because job seekers and companies know each others' contact information by this point, but I've heard of this happening to at least one company and one job seeker (separate events).

Sending false offer letters - Black hat recruiters will send out fake offer letters to job seekers for companies they're having trouble getting interviews for. Black hat recruiters rely on job seekers requesting to interview with the company before accepting the offer. The recruiter then arranges an interview with the company. If the company like the job seeker, the recruiter makes sure to process and negotiate the offer, sometimes issuing a "revised" offer to the job seeker. If there is not a fit for the job seeker at the company, the recruiter is no worse off than they started, and they just drop all contact with a job seeker.

If you're thinking that any of these practices might work for you, think again. Seriously. They may work in the short term, but you will do irreparable harm to your reputation, the reputation of job seekers, and the reputation of companies you represent in addition to possibly opening yourself up to legal problems.

If you're a company or a software engineer who's tired of dealing with these tactics, check out Hirelite: Speed Dating for the Hiring Process. We have another event next Tuesday.

Got any more horror stories? Leave them in the comments.