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Use sed to edit files in place (and make a backup copy)

Yesterday I ran into a situation where I had to edit 250,000 files, and of course I instantly thought of the Unix/Linux sed command. I knew what edit commands I wanted to run (simple swap/replace commands), but my bigger problem was how to edit the files in place.

A quick look at the sed man page showed that I needed to use the -i argument of the sed command:

By Alvin Alexander on December 11, 2011

How to find multiple filenames with Linux find

Linux find command FAQ: How can I write one find command to find multiple filenames (or filename patterns)? For example, I want to find all the files beneath the current directory that end with the file extensions ".class" and ".sh".

You can use the Linux find command to find multiple filename patterns at one time, but for most of us the syntax isn't very common. In short, the solution is to use the find command's "or" option, with a little shell escape magic. Let's take a look at several examples.

By Alvin Alexander on March 25, 2013

Handling spaces in Linux shell script input (and for loops)

Linux shell script FAQ: How can I deal with spaces (blank spaces) in my input data when I'm writing a shell script for loop or while loop?

I was just working on a Linux shell script, and ran into the ages-old problem of handling data that has spaces (space characters) in it. I run into this any time I try to read a data file with blank spaces in it, or when I run into files and directories with spaces in their names. Whenever I try to work this data like this in a shell script for loop, the spaces always ruin what I'm trying to accomplish.

By Alvin Alexander on May 4, 2013

Mac backups - handling spaces in filenames with find, tar, and xargs

This morning I decided to take a few minutes to backup all the songs I've purchased over the last half-year. These are all on my Mac OS X system, under the Music folder in my home directory.

The problem with trying to do this with standard Unix tools is that all these subdirectories and filenames have spaces in their names. Just looking at the Music folder, it contains many directory names like this:

By Alvin Alexander on October 20, 2012

Find command - Find files not matching a pattern

Unix/Linux find "patterns" FAQ: How do I find files or directories that don't match a specific pattern (files not matching a regex pattern, or filename pattern)?

In my case I just ran into a situation where I needed to find all files below the current subdirectory that are NOT named with the filename pattern "*.html" . Fortunately with the newer Unix/Linux find syntax this solution is pretty easy, you just include the "-not" argument, like this:

By Alvin Alexander on March 25, 2013

A Java FileFilter example

Summary: A Java FileFilter example, including a complete implementation of a Java FileFilter class.

I don't have much time for discussion today, but here's the source code for a Java FileFilter example I created in a text editor I wrote named "Jelly":

By Alvin Alexander on October 17, 2012

Java - How to list all files in a directory that match a filename extension

I just ran across this Java method I used to create a list of all files in a directory that match a specific filename pattern, or more specifically, matched the same filename extension.

The Java "list files in a directory" source code

First, here's the source code for this Java "list files" method. I'll follow this code with a brief description:

By Alvin Alexander on February 26, 2013

How to use multiple filename search patterns with Linux find

Linux find FAQ: How do I use the Linux find command to find multiple filename extensions (patterns) with one find command?

Problem

You want to use the Unix/Linux find command to search for multiple filename types (or patterns). You know you can run the find command several times, one for each filename extension you're looking for, but there must be a way to search for multiple filenames at one time.

By Alvin Alexander on April 14, 2013

Perl - How to process every file in a directory that matches a pattern

A common Perl FAQ is "How can I process every file in a directory that matches a certain filename pattern?"

There are several ways to do this, but I normally use the glob function, because I can remember the syntax pretty easily.

Let's look at a couple of glob examples.

Using the glob operator

You can use the glob operator to get a list of all files in the current directory like this:

By Alvin Alexander on August 6, 2011

A Perl temp file example

Many times in Perl applications you need to be able to create a temporary file (a Perl temp file). In this scenario you don't want to get into the system-specific details of temporary directories and things like that; you just want to create and use a temporary file.

Here are some Perl code snippets that should help get you started down this road.

By Alvin Alexander on August 8, 2011
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