Emacs startup time matters when you’re opening files frequently from the command line or in scripts. A few targeted optimizations can reduce perceived startup overhead from seconds to near-instant. Run Emacs as a daemon with emacsclient The most effective optimization is the server/client architecture. Start Emacs once as a daemon, then reuse that instance for…
When you run crontab -e, git commit, visudo, or similar commands, Linux applications need to know which text editor to launch. This is controlled by environment variables and system configuration, with several methods available depending on your needs. Understanding EDITOR and VISUAL The EDITOR environment variable tells applications which text editor to use. A related…
The built-in Print Screen workflow is cumbersome — capture, open Paint, paste, crop, save. There are better approaches depending on your needs. Snipping Tool and Snip & Sketch On Windows 7, the Snipping Tool is available through the Start menu. Press the Windows key, type “snipping tool”, and launch it. You get basic capture modes:…
When you need to combine multiple video files (like video1.mp4, video2.mp4, and video3.mp4) into a single output file, FFmpeg is the standard tool on Linux. It’s faster, more reliable, and better maintained than older tools like mencoder. Using FFmpeg with the Concat Demuxer The most robust approach uses FFmpeg’s concat demuxer, which properly handles file…
Finding large files is something you end up doing a lot — disk fills up, you need to track down what’s eating space, or you’re auditing a directory before archiving. The find command handles this cleanly. Basic usage Find all files larger than 500MB under the current directory: find . -type f -size +500M The…
This is fundamentally a decision about display technology and your reading habits. Here’s what you need to know. Display Technology The standard Kindle uses e-ink technology with a backlit display that requires external light sources — sunlight, a lamp, or overhead lighting. It’s readable but not ideal for low-light conditions. The Paperwhite adds a front-lit…
A4-sized PDFs—particularly technical papers and academic documents—render poorly on Kindle devices. The small fonts become nearly unreadable, and Amazon’s “Send to Kindle” feature often destroys formatting in the process. You need a tool designed specifically for this workflow. Why Standard Conversion Fails Amazon’s email-to-Kindle conversion assumes reflowable text content. Technical papers with multi-column layouts, equations,…
When you need to rsync against hosts behind NAT gateways or port-forwarded SSH services, the standard port 22 won’t work. The solution is the -e flag, which lets you specify a custom SSH command with your desired port. Basic usage Use -e to pass custom SSH arguments: rsync -avxP –delete -e “ssh -p 13022” username@example.com:/remote/path/…
When you work with multiple git servers or need different credentials for different hosts, SSH’s config file lets you specify which key to use for each server. This is cleaner than managing aliases or environment variables. Setting Up ~/.ssh/config Create or edit ~/.ssh/config and add entries for each server: Host git.example.org Port 22111 IdentityFile ~/.ssh/id_rsa.git.example.org…
utop is an improved OCaml REPL with line editing, history, context-sensitive completion, and syntax highlighting. While powerful, its key bindings differ from standard GNU readline, which can be jarring if you’re used to standard shell behavior. Getting the key bindings list The simplest way to see all available bindings is to run the #utop_bindings directive…
Trailing spaces and tabs at the end of lines are common annoyances in source code and configuration files. They’re invisible, waste space, and can cause issues with certain tools or version control systems. Here’s how to remove them efficiently. Using sed The most straightforward approach with sed: sed ‘s/[[:space:]]*$//’ your_file > your_file.tmp && mv your_file.tmp…
When deprovisioning Linux VMs in public cloud environments, disk blocks may be reallocated to other customers if the provider doesn’t properly wipe storage. This is a legitimate concern for security audits, compliance validation, and understanding data exposure risks. Quick Recovery Method The most straightforward approach uses dd and strings to extract readable data from block…
You have an LVM physical volume (PV) you need to remove from a volume group (VG), but the data needs to be preserved and moved to other available PVs. This is a straightforward but important operation that requires careful execution. Prerequisites Before starting, verify: The VG has sufficient free space on remaining PVs to accommodate…
When you need to execute a system command and capture its output in C, popen() is the standard approach. Unlike system(), which just runs a command, popen() gives you a file stream connected to the command’s stdout or stdin. Basic Usage The popen() function signature is: FILE *popen(const char *command, const char *type); The type…
When you need to format an integer with leading zeros in bash, printf is the standard approach. This is useful for generating zero-padded IDs, filenames, or any formatted output. Using printf The basic syntax mirrors C’s sprintf: n=42 str=$(printf “%08d” “$n”) echo “$str” # Output: 00000042 Here, %08d means: %d — format as decimal integer…
Start by compiling your C source files into object files: gcc -c lib1.c lib2.c This produces lib1.o and lib2.o. You can use any compiler flags here—-Wall, -O2, -fPIC, etc.—that match your build requirements. Position-independent code (-fPIC) isn’t strictly required for static libraries but is good practice if you anticipate reusing these objects elsewhere. Creating the…
Amazon’s Kindle Library web interface forces you to delete books one at a time through the UI. If you’ve accumulated hundreds of items, this becomes tedious. Here are practical approaches to bulk-delete from your Kindle Library. Browser Console Method The most straightforward approach uses your browser’s developer console to run deletion scripts directly against Amazon’s…
Setting environment variables in Bash is one of the most fundamental skills for working with Linux command lines and shell scripts. Bash provides several ways to define and manage variables. Setting a Variable for the Current Shell MY_VAR=”hello world” Important: No spaces around the = sign. MY_VAR = “value” will produce an error because Bash…
[md] Use setenv to set an environment variable in csh: setenv VARIABLE value Replace VARIABLE with the name of the variable and value with its value. The variable is immediately available in the current shell and inherited by child processes. ## Examples Set a simple variable: setenv PATH /usr/local/bin:/usr/bin:/bin setenv EDITOR vim setenv JAVA_HOME /usr/lib/jvm/java-17-openjdk…
Working with environment variables in C is straightforward using POSIX APIs. The two primary functions are getenv() for retrieval and setenv() for modification. Getting Environment Variables Use getenv() to read an environment variable: #include <stdlib.h> #include <stdio.h> int main(void) { const char *path = getenv(“PATH”); if (path != NULL) { printf(“PATH: %s\n”, path); } else…