linux

Using find and grep to print lines before and after what you're searching for

I just used this combination of a Unix/Linux find command with a grep command to search for all Scala files under the current directory that contain the string null. This command prints five lines before and after each null line in each file:

Linux find command: find and copy files

I ran into a situation this morning where I needed to use the Linux find command to (a) find all the MP3 files beneath my current directory and (b) copy them to another directory. In this case I didn't want to do a cp -r command or tar command to preserve the directory structure; instead, I wanted all of the files to end up in the same directory (so I could easily import them into iTunes).

A Scala shell script example (and discussion)

Scala shell script FAQ: How do I create a Unix/Linux shell script to run a small Scala script?

If you want to run a Scala script as a Unix or Linux shell script -- such as hello.sh -- write your script like this:

20+ Unix/Linux find command examples

Linux/Unix FAQ: Can you share some find command examples?

Sure. The Unix/Linux find command is very powerful. It can search the entire filesystem to find files and directories according to the search criteria you specify. Besides using the find command to locate files, you can also execute other Linux commands (grep, mv, rm, etc.) on the files and directories you find, which makes find extremely powerful. 

How to use curl to get headers from a URL

Curl FAQ: How do I use curl to get the headers from a website URL?

Short answer: Use curl's -I option, like this:

$ curl -I URL

Here's a specific example, including a real URL and results:

Teleport - the Unix/Linux cd command, improved

Summary: By keeping a history of the directories you've visited, the Teleport command is an improvement on the Unix/Linux cd command. By having a memory, Teleport lets you jump from one directory to any previously visited directory, easily.

A few quick notes:

Java exec - execute a system command pipeline in Java

In earlier articles I've described how to execute system commands from Java applications. A long time ago I wrote my first article on this topic (How to execute system commands from Java), and more recently I wrote an updated version of that article titled "Executing system commands from Java using the ProcessBuilder and Process classes".

Linux cut command example with field and delimiter

Should you ever run into a situation where you want to use the Linux cut command by specifying both a field number and field delimiter, I hope this example is helpful for you.

I was just working on a problem where I wanted to list all the fonts on a Mac OS X (Unix) system, and needed to use the cut command this way. A straight listing of all the filenames in the Mac font directory gave me a long list of names like this:

Show unique list elements with the Linux sort -u command

If you're ever working on a Unix or Linux system, and have a list with duplicated items in it, and want a smaller list of only the unique items in the list, the sort command is your friend.

I just ran into a situation where I generated a list of fonts on a Mac OS X (Unix) system, and my list ended up with a bunch of duplicated names, like this:

Debug Linux shell scripts with -x

If you ever need to debug a Unix or Linux shell script, you can just add the -x option to the interpreter when you invoke it. You can add the shell's debug option on the command line like this:

sh -x misbehaving_script.sh

or at the end of the first line in your shell script (the she-bang line), like this:

#!/bin/sh -x

I was just working on a shell script related to fonts on a Mac OS X (Unix), system, and when I tried to run it normally, all it gave me was this error message:

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